Previous: Using the InstallAnywhere Installer Table of contents Frames User guide
ITC-IDV Workshop for NGIC > Advanced Topics
5.3 Converting files to netCDF

Converting files to netCDF format requires specialized software: the UNAVCO File Converter is one amongst many. This program takes files in various, generalized formats and converts them to Unidata's NetCDF file format. NetCDF support multidimensional arrays of data and is a binary file format that stores metadata in the same file as the data, making every NetCDF file self-describing.

Though this conversion program can be used for any purpose, it was primarily designed to help researchers view geophysics data in Unidata's IDV, a 3D global visualization program. As a result, the data it accepts is highly selective towards geophysics views in the IDV.

The way the conversion process works is that first, a "configuration file" is created. This contains all the data that the program needs to convert the file and is stored on disk so it can be reused, even if you exit the program. Then you "execute" that file, which means actually converting the data. The program will help you create the file (you don't have to know how to do so yourself, just fill out the information it asks for). You then choose to execute that file and it will convert the data for you.

The result of this program being geared to the IDV is that it only accepts certain data. All data must have longitude and latitude, it can also have depth and time. And then, of course, it also has the data itself. The data can be anything, temperature, density, any scalar value.

  1. How to Run the Converter
    1. A tutorial for using the file converter
    2. Adding Attributes to the File
    3. Modifying Data Within a File
    4. Executing (Converting) a File
    5. Modifying a Configuration File
    6. Displaying a Converted netCDF File in the ITC-IDV
    7. Description of supported File Types
  2. List File Type
    1. Defenition of Type
    2. Example of Type
    3. Entering in MetaData
  3. Column File Type
    1. Defenition of Type
    2. Example of Type
    3. Entering in MetaData
  4. Labeled Column File Type
    1. Defenition of Type
    2. Example of Type
    3. Entering in MetaData
  5. Point File Type
    1. Defenition of Type
  6. Binary File Type
    1. Defenition of Type
    2. Entering in MetaData
  7. Track File Type
    1. Defenition of Type
    2. Entering in MetaData
  8. Frequently Asked Questions
    1. What do I do if the program hangs, or appears to hang?
    2. What if there is no time or depth?
    3. What if I have other variables?
    4. What if my file isn't in any of these formats?
    5. What if I have more than one file?
    6. What does the error: "Can not open file of type __" mean?
    7. What is an error occurring from "____.BuildClass()" or from"CConfigFile.CreateClass()" mean?
    8. What if I have multiple data variables?
    9. What effect does the "Positive is Below" setting have on the modification limits?
    10. If I don't have depth or time in my file, how does the Modify File Window work?
    11. To what extent can I modify a point file?
    12. My point file is not recognized in the IDV
    13. The data from my binary file looks wrong, what happened?
    14. What if the units in my file aren't the standard ones?
    15. Why is the number "1.7976931348623157E308" in the modify file pane?
    16. Why did the "Exit File Creator" button disappear and how can I exit now?"


How to Run the Converter

The first step in running the file converter is unpacking it. In Linux or Unix you should be able to use the "unzip" command to do this. In Windows, right click on the file (Converter.zip) and then select "Extract All".

No matter the operating system, you must have Java installed on your computer. You can download Java at Sun's website. Once you've downloaded Java you have all the tools you need to run the file converter.

If you're on Linux or Unix, then you can run the file converter with one line. Once you're in the appropriate directory (within the Converter folder) the following line should run the program:

java -Xmx512m -jar Converter.jar

If you're running Windows it is much simpler, simply double clicking the .JAR file or batch file "Converter.bat" in the directory where you unzipped the converter.zip file will begin running the program.

A tutorial for using the file converter



When you run the program a window will pop-up that looks like this:

Click on the "Create a Configuration File" button, a new window should pop-up that looks like this:

Along the top you'll a series of tabs. Each tab represents an interface for an individual file type. A "List File" will be the first option, click on the appropriate tab for you're file type. If your file is a column file, click on that tab and begin filling in the data. Some of the data will already be filled with zeros. Since some files can have depth and time data, but some wont, the zeros are the default values for that (if you leave the zeros there, it will assume you have neither depth nor time in your file).

Adding Attributes to the File

You can add attributes to the file. An attribute is NetCDF's way of storing metadata. Each variable can have attributes with any name added to it. The IDV recognizes certain attributes automatically, and uses them in displaying the data. A few of these are necessary, and those ones are included automatically in the file (the variable "lon" has a "long_name" equal to "Longitude" as an example). It's highly recommended that you leave the default attributes as they are, however, you don't have to do so. You can remove those attributes if you want, and it is perfectly acceptable to add on as many of your own attributes as you want. To do so, click on the "Open Attribute Window" button at the bottom of the configuration page. A window should pop up that looks like this:

If you've already modified this file (see below for modifying a configuration file), there may be different attributes there. If you want to revert to the default attributes, click on "Set Attributes to Default", but be careful, this will erase all the changes you've made permanently. If you see that there are attributes for time and depth when your file doesn't have those variables, don't worry, they will automatically be removed when the file is created (though you can manually remove them yourself if you wish to). To exit out of the screen simply click on "Return to Config File Creator".

It is very simple to add an attribute. Click on the "Add an Attribute" button, a window should pop up that looks like this:

First, select the variable you wish to add the attribute to. Your options for variables are: Longitude, Latitude, Depth, Time, and Data. The default selection is "Global", which is not a variable, and will be explained below. If your file is temperatures in the mantle, an example of adding an attribute would be to select "Data" as your variable, then type in "long_name" for the title of the attribute, and "mantle temperature" as your text. Or perhaps select Data, title of "units", and text of "Celsius".

As an example, another way of using the attributes page is to change the units for depth. They're automatically set to kilometers, but perhaps yours are in meters. To fix this, first go to the basic attribute panel and click "Remove Attribute" on the button next to the depth units attribute. This will remove that attribute from the file. Then click on "Add an Attribute" and fill out a title of "units" and text of "meters" for the Depth variable. Click on "Add Attribute", and now Depth will be read in meters instead of kilometers.

The Global attribute, is probably the one you'll use the most. Global doesn't assign a specific variable an attribute, rather the entire file gets that attribute. You may want to put in the file information detailing where it came from, this is a good use of the Global attribute. You would click "Add an Attribute", the variable will automatically be selected as Global, then enter a title of "source" and a text of "My Name created this file on August 23, 2004". Then add that attribute and your file will automatically contain the creation data within itself. The IDV will not recognize any global attributes, so feel free to use whatever title you want to label your file.

Modifying Data Within a File

The file converter, besides converting data into NetCDF, will also allow you to modify the data you have. You can limit the region you convert, and lower the resolution on that data. To begin, click on the "Open Window" button next to the words "Modify File Window". When you do, a window should appear that looks like this:

The first thing you may notice the large numbers in the fields; the default limits represent the widest possible range of values to keep from accidentally removing any data you don't want removed. You may change any or all of these values, which will tell the program what limits you want to put on latitude, longitude, depth and time. The depth and time limit selection can be found on the second panel (click on the tab at the top of the window labeled "Time/Depth" to get to this panel).

The other modification you're allowed besides limiting the area of data converted, is to lower the resolution. The lat/lon resolution is kept separate from the depth/time resolution (you could lower the resolution on the lat/lon grid by a factor of 2, and keep all of the depth and time resolution as is). The number you enter in the "Resolution" field represents the factor by which you wish to reduce the resolution. A factor of 1 will leave the resolution unchanged (and is the default value). A factor of 2 will skip every other datum on the lat/lon grid (or depth/time, if you're modifying the resolution in that pane). You can enter any number, 1 or greater, since anything less than one would be a meaningless resolution factor, the program will not accept negatives or zero.

To exit the modification window press the "Exit File Modifier" button in either pane. This will automatically save the changes you made and return you to the file configuration editor.

Executing (Converting) a File

Once you've filled out the data (for an explanation of each file type and what the data means, go here) click on "Save Configuration File As", if you want to stop creating a configuration file and don't want to save the one you're working on, click on "Exit File Creator".

If you do save your file, a file browser will pop up and ask you for the file name. The extension ".conf" will automatically be appended onto your file choice. When the file browser exits, the file has been saved and you're returned to the configuration file creator. To execute the file you just created, exit the configuration file creator. The original screen has a button labeled "Execute a Configuration File", click on that. Then use the file browser that pops up to select the configuration file you just created (or any other configuration file you would like to execute).

Once you select the file, the program will begin converting the data. This may take some time, please be patient. A bar will pop up alerting you that the file is being converted, it will disappear when the process is over. To leave the program click the "Exit" button at the bottom of the original window.

Modifying a Configuration File

You can choose to modify a previous configuration file rather than create it from scratch. Simply click on "Modify a Configuration File", then select the file you would like to modify. The file configuration creator will open with your file loaded into the appropriate tab.

Displaying a Converted netCDF File in the ITC-IDV

Now we have converted a file into netCDF we can start displaying it using the IDV.
  1. Open the IDV Dashboard.
  2. Click on the Files Tab and browse to your new netCDF data file and click Add Source.
  3. In the Field Selector Tab you will now see a new data source. Select a variable, times, region and choose a desired Display type as shown below.Display new netCDF data source
  4. Click Create Display.

Description of supported File Types

You can choose from the following supported file types.

List File Type

Defenition of Type


A list file is essentially a list of data. It should contain no metadata, or dimensions (like longitude and latitude). The data can be separated in any way, commas, spaces, both, any way that has a non-numeric character (or ‘E', which is considered to be part of the number: 1.043E+-01).

All the dimensional data will have to be entered in another way. This program assumes that all dimensions (latitude, longitude, depth, time) are evenly spaced in the file (if there's a 2 degree gap between the first two longitudes, there must always be a 2 degree gap between longitudes). So you are required to enter some information about the dimensions and then the program will automatically generate them for you. Entering in the information is explained below.

Example of Type

-0.56899E+00 -0.56699E+00 -0.56499E+00 -0.56399E+00 -0.56199E+00 -0.56099E+00 -0.55999E+00 -0.55899E+00
-0.55899E+00 -0.55799E+00 -0.55799E+00 -0.55799E+00 -0.55799E+00 -0.55799E+00 -0.55799E+00 -0.55899E+00

Entering in MetaData


Below is a picture of the panel for entering the required metadata on a list file:

The first two requirements are common to all file types, a file to be converted and a file to be created. Use the browse button next to these fields to select the desired files.

The next four fields ask for the number of longitudes, latitudes, depths and times. Longitude and latitude are both required dimensions, so you must enter non-zero values for these fields. A file can be successfully converted without depth and time, and if the file you wish to convert doesn't have one or both of these, then simply enter in ‘0' for the number of that dimensions. 0s will be automatically entered in by the program for each non-required variable, so you can simply leave those fields untouched.

The next 8 fields ask for a description of the dimensions so it can create them. If your data starts at 90N/0E/-460km depth, you're start would be 90 for latitude, 0 for longitude, -460 for depth and 0 for time.

The "space" fields ask for the distance (in appropriate units) for each of the dimensions. If there's always a 4 degree space between latitude (meaning the next latitude after 90 would be 86) then enter -4. Positive and negative are very important, the program adds the space number always. For depth, remember that it defaults to positive being up, so if you're depth goes from -460 to -520, the space would be -60.

The final field unique to the list file is the "Does the latitude changes faster than the longitude" field (with the option of either yes or no). All files are assumed that first the latitude and longitude cycle through, then the depth, then the time, but latitude and longitude can go in any order. If the dimensions go from 90N/0E/-460km to 86N/0E/-460km then the answer would be yes, since the latitude changes before the longitude. If it started at 90N/0E/-460km and went to 90N/2E/-460km then the answer would be no.

The final fields are common to all file types. The "Is positive depth above or below ground" question (with answer choices above and below) simply means that if the file starts 460km below the surface of the Earth, and you entered in "460" as you're starting point, then positive would be below the surface. This option can also be changed (with extra work) through the attributes panel, but it is common enough to be a general option on the main panel. The attributes panel is explained fully in the user's guide.

Column File Type

Defenition of Type


86   270   3.0

A column files is one in which each data value also has a latitude and longitude associated with it on one line (depth and time being optional). For instance, a line may look like this:

86   270   3.0

Column 1 (86) stores the latitude for that data point, column 2 (270) stores the longitude, and column 3 (3.0) stores the data value itself. The whole file is simply line after line in this format. The columns can be arranged in any way, data first would be acceptable for instance. Also, the program will automatically ignore any extraneous columns.

Example of Type

1   90   0   -460   3   1.02
2   86   0   -460   3   3.12
3   84   0   -460   2   0.34
4   80   0   -460   3   6.89
5   76   0   -460   1   0.07
  
1 90 0 -460 3 1.02
2 86 0 -460 3 3.12
3 84 0 -460 2 0.34
4 80 0 -460 3 6.89
5 76 0 -460 1 0.07


Column 1 is simply the line number, column two is the latitude, column 3 is the longitude, column 4 is the depth, column 5 is the accuracy of the data and column 6 is the data itself.

Entering in MetaData


Below is a picture of the panel for entering the required metadata on a column file:

The first two requirements are common to all file types, a file to be converted and a file to be created. Use the browse button next to these fields to select the desired files.

The only fields unique to the column file are the following 5 fields. They ask for the column number for each variable, 0 if that variable doesn't exist (the default for depth and time). In the example snippet above, a 2 would be entered for latitude, 3 for longitude, 4 for depth and 6 for data. The fact that columns 1 and 5 are unnecessary doesn't effect the rest of the data, and there is no need to eliminate them.

The final fields are common to all file types. The "Is positive depth above or below ground" question (with answer choices above and below) simply means that if the file starts 460km below the surface of the Earth, and you entered in "460" as you're starting point, then positive would be below the surface. This option can also be changed (with extra work) through the attributes panel, but it is common enough to be a general option on the main panel. The attributes panel is explained fully in the user's guide.


Labeled Column File Type

Defenition of Type


A column files is one in which each data value also has a latitude and longitude associated with it on one line (depth and time being optional). For instance, a line may look like this:

86   270   3.0

Column 1 (86) stores the latitude for that data point, column 2 (270) stores the longitude, and column 3 (3.0) stores the data value itself. The whole file is simply line after line in this format. The columns can be arranged in any way, data first would be acceptable for instance. Also, the program will automatically ignore any extraneous columns.

A Labeled column has names at the top of each column, the program will automatically read in the labels and check the names for matches (lat for latitude for instance). The labels must not have any spaces in them (for example, a label like "Depth beneath Surface" would cause errors, simply put "Depth").

Example of Type

Line	Latitude	Longitude	Depth	Accuracy	Data
1	90		0		-460	3		1.02
2	86		0		-460	3		3.12
3	84		0		-460	2		0.34
4	80		0		-460	3		6.89
5	76		0		-460	1		0.07
  

Column 1 is simply the line number, column two is the latitude, column 3 is the longitude, column 4 is the depth, column 5 is the accuracy of the data and column 6 is the data itself.

Line Latitude Longitude Depth Accuracy Data
1 90 0 -460 3 1.02
2 86 0 -460 3 3.12
3 84 0 -460 2 0.34
4 80 0 -460 3 6.89
5 76 0 -460 1 0.07


Entering in MetaData


Below is a picture of the panel for entering the required metadata on a column file:

The first two requirements are common to all file types, a file to be converted and a file to be created. Use the browse button next to these fields to select the desired files.

There is no data to enter unique to the labeled column. Each column should be labeled within the file itself, and thus no data is needed for the file in general about which column is which. However, the labels must be appropriate, as was mentioned above, no label can have a space in it or it will be taken as a new label and the numbering of columns will be off. Second, there are specific labels accepted, they are not case sensitive, but your labels must match with one of these labels or the program wont recognize the name.

Latitude Latitude, Lat
Longitude: Longitude, Lon
Depth: Depth, Dep, Lay, Layer, Lev, Level, Height, Elevation, Elv
Time: Time, timeObs, Seconds, Sec, Secs
Data: Data, Dat, Variable, Var

The final fields are common to all file types. The "Is positive depth above or below ground" question (with answer choices above and below) simply means that if the file starts 460km below the surface of the Earth, and you entered in "460" as you're starting point, then positive would be below the surface. This option can also be changed (with extra work) through the attributes panel, but it is common enough to be a general option on the main panel. The attributes panel is explained fully in the user's guide.

Point File Type

Defenition of Type


A point file is one in which the data is not spaced out on a grid, but rather at arbitrary points around the world. This requires that every data point must have a latitude, longitude, depth and time (depth and time are required for point files in the IDV, but if a file doesn't have them the converter will automatically add them). A point file must be in exactly the same format as a column file, and all metadata required is the same.

A description of the column format and entering the metadata for it is here. Below is a picture of the form for entering metadata for a point file:


Binary File Type

Defenition of Type


A binary file is very similar to a list file, the only data in the file should be the variable data, no headers and no latitudes, longitudes, depths or times. A sequential list of data values, stored in binary format with no delimiters in between them.

All the dimensional data (latitude and longitude for instance) will have to be entered in another way. This program assumes that all dimensions (latitude, longitude, depth, time) are evenly spaced in the file (if there's a 2 degree gap between the first two longitudes, there must always be a 2 degree gap between longitudes). So you are required to enter some information about the dimensions and then the program will automatically generate them for you. Entering in the information is explained below.

Entering in MetaData


Below is a picture of the panel for entering the required metadata on a list file:

The first two requirements are common to all file types, a file to be converted and a file to be created. Use the browse button next to these fields to select the desired files.

The next four fields ask for the number of longitudes, latitudes, depths and times. Longitude and latitude are both required dimensions, so you must enter non-zero values for these fields. A file can be successfully converted without depth and time, and if the file you wish to convert doesn't have one or both of these, then simply enter in ‘0' for the number of that dimensions. 0s will be automatically entered in by the program for each non-required variable, so you can simply leave those fields untouched.

The next 8 fields ask for a description of the dimensions so it can create them. If your data starts at 90N/0E/-460km depth, you're start would be 90 for latitude, 0 for longitude, -460 for depth and 0 for time.

The "space" fields ask for the distance (in appropriate units) for each of the dimensions. If there's always a 4 degree space between latitude (meaning the next latitude after 90 would be 86) then enter -4. Positive and negative are very important, the program adds the space number always. For depth, remember that it defaults to positive being up, so if you're depth goes from -460 to -520, the space would be -60.

The next field is "Does the latitude changes faster than the longitude" field (with the option of either yes or no). All files are assumed that first the latitude and longitude cycle through, then the depth, then the time, but latitude and longitude can go in any order. If the dimensions go from 90N/0E/-460km to 86N/0E/-460km then the answer would be yes, since the latitude changes before the longitude. If it started at 90N/0E/-460km and went to 90N/2E/-460km then the answer would be no.

The next two fields ask how the binary data is formatted. The first field asks what type of data it is. Byte (for C and C++ users, this is equivalent to "char"), unsigned byte, short, integer, long (this is twice the size of the integer, 64 bits), float, and double. The bits of each type are listed in the drop-down menu, but watch out, except for the unsigned byte option, all of the data values must be signed, if they are unsigned, they will not be properly dealt with by the program. Also note that the float and double variables must be in IEEE 754 format, if you don't know what that means you probably don't have to worry about it, this is the standard floating point format.

The second field asks about the "endian-ness" of the data, what the endian byte format is. What this means is what order the bytes are in. Big endian (or as you may know it, MSB) has the "most significant" byte first, or the byte that has the largest impact on the magnitude of the value. Little endian has the bytes in the opposite order (you may know this format as LSB). Java will always create big endian files, C and C++ on the PC will create little endian files, you'll have to determine which type your file is; if you don't know the easiest way may be to try both and see which one works (looks right).

The final fields are common to all file types. The "Is positive depth above or below ground" question (with answer choices above and below) simply means that if the file starts 460km below the surface of the Earth, and you entered in "460" as you're starting point, then positive would be below the surface. This option can also be changed (with extra work) through the attributes panel, but it is common enough to be a general option on the main panel. The attributes panel is explained fully in the user's guide.

Track File Type

Defenition of Type


The track file is a file that will show a series of data points along a line (which does not have to follow any pattern or linearity). Each point can have a data value associated with it and the line will be colored by the IDV based on these values. It must be noted that the IDV requires a specific naming convention to recognize that the file is a track file (otherwise the file will not be parsed correctly). An appropriate name might be "WMI_Lear" followed by any desired name, "WMI_Lear-TrackFile.nc" for example.

The file type should be in the same form as the Column file, rows of data. The data doesn't have to have any specific order to it (increasing longitude or latitude), but the line will be drawn sequentially from point to point.

Entering in MetaData


Below is a picture of the panel for entering the required metadata on a track file:

The first two requirements are common to all file types, a file to be converted and a file to be created. Use the browse button next to these fields to select the desired files.

The next following fields are identical to the Column fields. The track file is set-up with exactly the same structure of the column file, each data point is represented by one line in the file which will have all the necessary information (latitude, longitude, depth, time and the data value itself). If the user has no depth or time values that is acceptable, but it should be noted that a track file must contain time, and thus the program will automatically insert a time value that will start at 1970 and increment by one second for each data point.

These data fields should be completed in the same manner that would be done if this where a column file. Either enter zero if the data is not part of the file, or enter in the appropriate column (starting the numbering from zero) where the data lays. Extraneous columns do not hamper the program from converting your data, but any extraneous lines within the data will not be dealt with properly and either a faulty file will be create or the program will report an error.

The final fields are common to all file types. The "Is positive depth above or below ground" question (with answer choices above and below) simply means that if the file starts 460km below the surface of the Earth, and you entered in "460" as you're starting point, then positive would be below the surface. This option can also be changed (with extra work) through the attributes panel, but it is common enough to be a general option on the main panel. The attributes panel is explained fully in the user's guide.

Frequently Asked Questions

What do I do if the program hangs, or appears to hang?


The first solution to this problem is try to be patient. The converter can take a long time with some of the larger files, and will often times appear to hang when really it's doing it's job just fine,. Unfortunately, often times it will simply stop working without giving an error message or changing it's appearance. If you've feel this has happened try clicking the "Exit" button on the original screen, if the program has hung this will almost certainly stop it.

If it does hang the overwhelmingly most likely possibility is that it ran out of memory, the program is very memory intensive, and even moderately sized files can cause high memory usage. Java programs default to being able to use only a small amount of memory. If you're file is around 100MB or larger, this could be an issue, or if you have less than 512MB of RAM on your computer.

What if there is no time or depth?


Latitude and longitude are both required for the program to run, but time depth are always optional. When creating a configuration file the defaults for time and depth will be zero, if you leave the fields that are filled in as they are then it will assume no time or depth. For specifics on how to define no time or depth see the different file types.

What if I have other variables?


The only variables allowed are latitude, longitude, depth and time. It also only allows one data type (for instance, if a file had both temperature and density on a grid, only one of those data types could be saved). If the file is in column form then the program will ignore them, if they make up a dimensions (if the data changes along latitude, longitude, and this other dimensions that is neither depth nor time) then the conversion will create faulty data.

What if my file isn't in any of these formats?


The most generic, basic file formats were picked for this program, ones that were found commonly among various data that were converted. However, it is quite likely that your data format will differ, perhaps slightly, from all of these different types. If this is the case you can do one of three things:
1) Write a add on to this program that will convert your file type (see creating a file type). This is time-consuming and complicated, and unless you anticipate widespread use of your file format, probably not worth it.
2) Not use this program and convert the file to NetCDF, or to CDL and then NetCDF yourself. This is certainly possible, but the reason this program was created was because of the difficulty of mastering the NetCDF format (or CDL format). If you do choose this path, you may wish to go to Unidata's NetCDF site.
3) The preferred approach would be to convert your data into a format that this program does understand. Most likely this will be by far the simplest and fastest route to converting your data to NetCDF. The formats that can be handled are quite basic and straight forward, converting to them should be a quick process.

What if I have more than one file?


Unfortunately the file converter can only take one input file. If you have multiple files that you want to append, or one for each depth sample or something similar you will have to turn them into one file yourself.

What does the error: "Can not open file of type __" mean?


This is an error from the configuration file you selected. It means that the file type listed in the configuration file is not a type the converter recognizes (it's a number between 1 and however many different file types can be converted). Check the configuration file to make sure that the very first line ends in a colon followed by a space and the appropriate number.

What is an error occurring from "____.BuildClass()" or from"CConfigFile.CreateClass()" mean?


Most likely an error of "null" was returned for this error. It means that there was some error reading the configuration file, most likely that a line is either missing or is in not in proper format. To avoid this error, try re-creating the configuration file using the program's interface. If you want to try and fix this manually, remember that the configuration file's data is either attributes, or ends in a colon, a space, and whatever data is on the line.

What if I have multiple data variables?


Sorry, only one variable at a time with the file converter. If your data is in column form, it is very easy to create a different file for each variable (simply change the column number for the data variable), but you can not create one file with all the variables in it. This is allowed by both NetCDF and the IDV, so if you wish to create such a file it is practical, but you'll have to use tools besides this program.

What effect does the "Positive is Below" setting have on the modification limits?


The file converter makes the change of depths (if "Positive is Below" is set) after modifying the data. That means that if your file has depths from 20 to 30, labeled as positive in your file and you want to only have 22-28, you should use positive 22 and positive 28 as your limits, even though they will eventually be changed to negatives.

If I don't have depth or time in my file, how does the Modify File Window work?


The Modify File window will always allow you to change both the limits and resolutions, even if the data that they're supposed to be affecting isn't there. So you can change the range of time allowed even in a file that has no time (though this would be a waste of your time). The resolution field in the depth/time window will have an effect on whichever one exists. For instance, if you have depth in your file, but no time variable, setting the resolution to ‘2' in the depth/time pane will still filter out every other depth, and same would go for only time and no depth.

To what extent can I modify a point file?


A point file can be partially modified through the "Modify File" window, the limits on latitude, longitude, depth and time can be set and will filter out any data not within those limits. However, though the resolution field can still be changed, it will have no effect on the data.

My point file is not recognized in the IDV


The IDV recognizes point files by the file name. They must end in _eq.nc, if your file name does not, the IDV will not know that it is point data. Also, point data currently only works in GEON's version of the IDV, if you're using the version downloaded from Unidata it will not recognize point data no matter what.

The data from my binary file looks wrong, what happened?


When converting a binary file, you must make sure that the data types you specified are exactly right, or you can get a bad file output without any run-time errors. Some common pit-falls to watch for are the "endian-ness" of the file, the data type and size used, and making sure that the data is signed (unless it's unsigned bytes). For more information and a more detailed explanation, see the binary file description.

What if the units in my file aren't the standard ones?


Both NetCDF and the IDV allow for various units (NetCDF allows for any units, and the IDV has a specific set that it will recognize). The file converter defaults to standard units, depth in kilometers, latitude in degrees north ("degrees_north"), longitude in degrees east ("degrees_east"), and time in "seconds since 1970-01-01 00 UTC". Any of these may be changed by the user, though you should take care to use units that the IDV recognizes or it will not properly display your file, should it display it at all.

You can change the units by opening the attribute window in the file creator pane, then click on "remove attribute" by the unit you will be changing. Then click on "add attribute", and select the appropriate variable whose unit you're setting, then set the title to "units" and the text to the unit itself. For example, to change longitude to degrees west, remove the "lon", "units", "degrees_east" attribute from the attribute pane, then add an attribute to the variable "lon", titled "units", and with a value of "degrees_west", and click on add attribute. The file will now store longitude as being in degrees west.

You may set the data variable units (the "var" in the attribute pane) to any that you wish. The IDV will recognize certain units and not others, but will display even those units that it doesn't recognize, or one with no units at all, which is the default for the file converter.

Why is the number "1.7976931348623157E308" in the modify file pane?


The file converter defaults to having this number as it's maximum, and it's negative as it's minimum for all of the different variable (lat, lon, depth and time). This number is the maximum value that the variables can be, and thus, by definition, includes every possible variable. This is designed to make sure that the default values do not exclude any of the data you put in. These values can be changed if you do wish to limit the area converted in your file.

Why did the "Exit File Creator" button disappear and how can I exit now?"


When the width of the window becomes too small, the exit button can disappear, all that you need to do is make the window larger and it will come back. Or, if you want to keep the window that size, clicking the ‘x' in the upper right of the window serves exactly the same function as the exit button (it doesn't do any harm to use that button to exit).


Previous: Using the InstallAnywhere Installer Table of contentsFrames User guide
ITC-IDV Workshop for NGIC > Advanced Topics