OziExplorer 3D - Sources of Digital Height Data

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This is the best data to use for most countries.  (See the section below for a 2014 update)

SRTM (Shuttle Radar Topography Mission), a joint project between the NIMA and NASA to produce digital topographic data for 80% of the Earth's land surface (all land areas between 60º north and 56° south latitude).

Most of the world has been released on a 3-arc-second (approximately 90 meters) grid, with the USA data being available on a 1-arc-second (approximately 30 meters) grid.

Note: Also available for download is SRTM30 (approximately 1km grid) comprising a combination of data from the Shuttle Radar Topography Mission, and the the U.S. Geological Survey's GTOPO30 data set. It is formatted the same as the GTOPO30 convention so should be considered as GTOPO30 data (see below).

(OziExplorer version 3.95.3a or later is required to read SRTM data. A new version can be downloaded from the OziExplorer webpage. Older versions of OziExplorer will not detect SRTM data.)

Downloading

Note: OziExplorer version 3.95.4j or later has the ability to download SRTM height data for the region of map being viewed so manual downloading through the site shown below is not required. The SRTM Download option is on the 3D/Elevation Menu. (OziExplorer3D must be installed for this menu to be visible.)

• Download - SRTM data for some regions can be downloaded from here (SRTM1 - USA; SRTM3 - World).

Note : The file names represent the bottom left corner of your map, check your map to make sure you obtain the correct files. The naming convention of the files is "N49W110.hgt", for example this file covers the region from 49-50 deg North and 109-110 deg West.  In the southern hemisphere, the file "S17E142.hgt" covers the region 16-17 deg South and 142-143 deg East.

If you have downloaded the data for your area but OziExplorer does not display any heights , downloading the wrong files is the most likely cause, double check that you have downloaded the correct data files.

The SRTM data has artifacts, this is particularly noticeable over water (lakes or rivers) and where sharp changes in height occur.

Using the Data

• The files have a .zip extension indicating they are a compressed file. A program called oziUnGzip.exe is supplied with OziExplorer3D which can uncompress these files.

• Run the oziUnGzip program and select the file (or files) you want to extract, they will be extracted to the same folder as the compressed file. Note - You must use version 1.1 of the oziUnGzip program (the version is in the program caption - version 1.0 does not display a version number).

• The file extracted will have the extension .hgt.  Important - Do not change the file name of the .hgt file as it is used to position the dem.

• Place the file in the "Globe (Arcview)" Elevation Data folder.

• OziExplorer must be configured to use SRTM data by configuring the use of Globe Data in Elevation Configuration (see the Help file for details).  If you have not configured this path then you must do that before the height data will be used.

• If you no longer want the original .zip then you can delete it manually using windows explorer.

late 2014. Data generated from NASA's Shuttle Radar Topography Mission (SRTM) in 2000 will be released globally over the next year at 1 arc-second, or about 30m sampling that reveals the full resolution of the original measurements. Data for most of Africa and its surrounding areas were released with the announcement. The next release is planned for November 2014, and it is expected to include all of South America and North America, most of Europe, and islands in the eastern Pacific Ocean.

This data can be obtained from the site below and used in OziExplorer.  (LOGIN is required to download data - it is easy to create an account)

http://gdex.cr.usgs.gov/gdex/

• Move and zoom to your region

• Select "Define Rectangle Area" button and draw area on the map
  (max 36 tiles at one time.  Eg: Spain would need to be downloaded in 2 sections)

• Tick the "NASA SRTM 1 arcsec" box (the regions available will change color)

• Select "Download Data for Defined Area" button (hover mouse over the buttons for Hint)

• On the Download dialog, select the following -

• Product - NASA SRTM V3.0, 1 arcsec

• Format - ArcASCII

• Projection - Lat/Lon

• Select "Submit"

• Unzip the download to the OziExplorer\Elevation Data\Grid Ascii folder.

In PC OziExplorer, 3D Configuration, configure the path to the data and select it.

NGA (NIMA) DTED is a global Digital Terrain Elevation Database (DTED) provided by the National Imagery and Mapping Agency (USA) with a horizontal grid spacing of 30 arc seconds (approximately 1 kilometer).
 

The NGA DTED data can be downloaded from the NGA Raster Roam page here NGA DTED Data for most of the World. (Free download)

• When you open the web page you will see a map of the World with many options.

• In Desired Product Level, select "DTED Level 0".

• Click on the image at the required Lat/Lon and wait for the next page to be displayed, centered on these coordinates.

• Go to the Raster Exporter section at the bottom of the page.

• If necessary, change the coordinates in the boxes showing the "bounding rectangle" to adjust the selected area.

• There is a limit on the amount of data you can download at one time.

• When you have the area selected, click on the Raster Exporter button.

• The data file will be compiled and the "Raster Roam Requested Download File" web page with the file download link.

• Click on the link and Save the file to a folder on your hard disk.

• It is suggested you download the files to a folder called \Elevation Data\DTED located under the folder where OziExplorer is installed.

Using the Data

• The files have a .zip or .tar extension indicating they are a compressed file. A program called oziUnGzip.exe is supplied with OziExplorer3D which can uncompress these files. If you want to use Winzip to uncompress tar files you must turn OFF the smart carriage return linefeed conversion otherwise the data is destroyed.

• Run the oziUnGzip program and select the file (or files) you want to extract, they will be extracted to the same folder as the compressed file. Note - You must use version 1.1 of the oziUnGzip program (the version is in the program caption - version 1.0 does not display a version number).

• The DTED data contains many files that are not required by OziExplorer so these are automatically deleted. Only the .dt0 files are kept (or dt1 or dt2).

• If you no longer want the original .zip or .tar file then you can delete it manually using windows explorer.

• The uncompressed DTED data files must be placed in the NIMA DTED path that you have configured OziExplorer to point to in Elevation Configuration (see the Help file for details).  If you have not configured the NIMA DTED path then you must do that before the height data will be used. If your OziExplorer does not have a NIMA DTED path then you need to download a later version.

• Note - The DTED data is stored in numerous folders, a separate folder for each 1 degree of longitude. Within each folder numerous .dt0 files are placed, 1 file for each 1 degree of latitude. The files must be left in this structure. The folders must be directly attached to the NIMA DTED path you configured in Elevation Configuration, if not they will not be found.

• Caution - The data will be extraced into a new folder called dted (its part of the path stored with each file in the zip) so be aware that you may end up with path which ends with /dted/dted, if this happens make sure the DTED path in Elevation Configuration includes both the names (example C:\OziExplorer\Elevation Data\dted\dted)

• After adding new height data files to OziExplorer you must restart OziExplorer or go into Elevation Configuration and press the Save button to force the new files to be scanned.

Level 1 and level 2 Data

The data available to the public is called Level 0 and has a 30 arc second spacing.

Other higher resolution data called Level 1 and Level 2 is not available to public but can be used in OziExplorer if you have it by making sure the DTED path name ends in a 1 or a 2 ( example \dted1 ) depending on the level you are using. OziExplorer uses the last character in the path name to determine the files to search for ( .dt1 or .dt2 ). Note the use of Level 0 data does not require a special folder name.
 

The Gtopo30 data can be downloaded from from EarthExplorer website here GTOPO30 DEM Data for most of the World. (Free download but login required) The Gtopo30, SRTM and SRTM void filled can be downloaded but it is highly recommended first using the SRTM download built into OziExplorer on the 3D/Elevation Menu.

• From the web site, login and then zoom in the map to the required region.

• Click the "Use Map" button to select the region.

• Click the "Datasets" button to display a list of datasets.

• Click the + button nect to the Digital Elevation dataset.

• Select the GTOPO30 data

• Click the "Results" button.

• Select the dataset and click the "Download" button (disk drive with down arrow)

• IF you have not already logged in, you will be asked to login to download.

Using the Data

• GTOPO30 :

• The files have are zipped (.zip extension) An unzip program like Winzip is used to unzip the files to the "GTOPO30" folder under the "OziExplorer\Elevation Data" folder.

• The Gtopo30 data contains a large .src file, this file is not required by OziExplorer (and probably not by any other software) so it is automatically deleted. The files required by OziExplorer are the .DEM and .HDR files, any other files can be deleted if you wish. 

• If you no longer want the original .zip file then you can delete it manually using windows explorer.

• The uncompressed Gtopo30 data files must be placed in the Gtopo30 path that you have configured OziExplorer to point to in Elevation Configuration (see the Help file for details).  If you have not configured the Gtopo30 path then you must do that before the height data will be used.

• After adding new height data files to OziExplorer you must restart OziExplorer or go into Elevation Configuration and press the Save button to force the new files to be scanned.

• SRTM : If this dataset is downloaded from this site, select the DT2 option and follow the instructions for the Level 2 data in DTED section above. If BIL format is downloaded, see the GLOBE (Arcview) section above.

The Global Land One-km Base Elevation (GLOBE)
The GLOBE project has developed a quality-controlled global Digital Elevation Model (DEM) with a 1 Kilometer spacing (approx).

The Globe data can be downloaded from here GLOBE Data for most of the world. (Free download)

• Select the option Select your own area. link under the Data heading, this will take you to a page where you can specify the region you want to download (Java is required on your browser).
  (NOTE: Do not use the "Any or all 16 "tiles" link to download data. Data downloaded via this graphical interface is NOT compatible with OziExplorer.)

• You can Choose Your Type Of Area Selection as the "Text Entry" or the "Map-based (uses a Java applet)", both will produce the same type of files.

• You MUST use the following settings to produce data in the correct format

  • Export Type ESRI ArcView

  • Data Type int16

  • File Format PC binary

  • Compression Option Compressed tar file

  • Transfer Option FTP

  • Enter a different File Name and Unique Name if desired.

• Press the Get Data button to create the data files, there will be a delay while the files are created.
• When complete click on the link "click here" to download the data files

• It is suggested you download them to the \Elevation Data\Globe folder located under the folder where OziExplorer is installed.

Using the Data

• The files have a .tgz extension indicating they are a compressed tar file. A program called oziUnGzip.exe is supplied with OziExplorer3D which can uncompresss these files. If you want to use Winzip to uncompress these files please read the warning on the Globe web site.

• Run the oziUnGzip program and select the .tgz file (or files) you want to extract, they will be extracted to the same folder as the .tgz file.

• If you no longer want the original .tgz file then you can delete it manually using windows explorer.

• The uncompressed Globe data files must be placed in the Globe (ArcView) path that you have configured OziExplorer to point to in Elevation Configuration (see the Help file for details). If you have not configured the Globe (ArcView) path then you must do that before the height data will be used.

• After adding new height data files to OziExplorer you must restart OziExplorer or go into Elevation Configuration and press the Save button to force the new files to be scanned.

The 250K data can be downloaded from here USGS Geographic Data Download  (Free download)

• Click on the alphabetical list to obtain the data for the region you want

• It is suggested you download the files to the \Elevation Data\USADem250 folder located under the folder where OziExplorer is installed.

Using the data

• The files have a .gz extension indicating they are a Gzip compressed file. A program called oziUnGzip.exe is supplied with OziExplorer3D which can uncompresss these files.

• Run the oziUnGzip program and select the .gz file (or files) you want to extract, they will be extracted to the same folder as the .gz file.

• If you no longer want the original .gz file then you can delete it manually using windows explorer.

• The uncompressed USA Dem 250K data files must be placed in the USA DEM 250 path that you have configured OziExplorer to point to in Elevation Configuration (see the Help file for details). If you have not configured the USA DEM 250 path then you must do that before the height data will be used.

• After adding new height data files to OziExplorer you must restart OziExplorer or go into Elevation Configuration and press the Save button to force the new files to be scanned.

Download from GISDataDepot.com (or other source). Once you have selected your region, select "Digital Elevation Models (DEM) - 24K" and download the compressed file. (Free download)

Files size vary from 300K to 4MB

Download for Alaska from USGS - This data is 15 minute for Alaska and will work with OziExplorer, unzip the .dem files to a folder and configure the path in 3D configuration as USA DEM 24K.

• Click on the map to obtain the region you want

• This will take you to a detailed list of regions, click on the region you want

• This will present you with a list of files which cover the region, to save download time only download the compressed files.

• It is suggested you download them to the \Elevation Data\USADem24 folder located under the folder where OziExplorer is installed.

Using the data

• The files have a .DEM.SDTS.TAR.GZ extension indicating they are a Gzip compressed file. The files are also in the SDTS format, for OziExplorer to use them they must be in the DEM format. A program called oziUnGzip.exe is supplied with OziExplorer3D which can :

  • uncompresss the files

  • extract the files from the TAR file

  • convert the SDTS files to a DEM file

  • the TAR and SDTS files are automatically deleted after being converted
     

• Run the oziUnGzip program and select the .gz file (or files) you want to extract, they will be extracted to the same folder as the .gz file.

• If you no longer want the original .gz file then you can delete it manually using windows explorer.

• The uncompressed USA Dem 24K data files must be placed in the USA DEM 24K path that you have configured OziExplorer to point to in Elevation Configuration (see the Help file for details). If you have not configured the USA DEM 24K path then you must do that before the height data will be used.

• After adding new height data files to OziExplorer you must restart OziExplorer or go into Elevation Configuration and press the Save button to force the new files to be scanned.

This should be the best data to use for Australia.

The data that has been released is 3-arc-second (approximately 90 meter grid).

See the instructions above in the "SRTM" section on how to use the data.
 

Our testing shows that for Australia this data is much better than the Gtopo30 and the Globe data. (approximately 1 kilometer grid)

See the instructions above in the "World" section on how to use the data.
 

Both the GTOPO30 and GLOBE data (see World section above) covers Australia. (approximately 1 kilometer grid)

See the instructions above in the "World" section on how to use the data.
 

GEODATA 9 Second DEM Version 2 is no longer available on CD. (Note:  This data can also be downloaded from the Geoscience Australia website but the data which is downloaded is NOT in a suitable format that can be used directly by OziExplorer).

The grid spacing is based on geographic coordinates at a maximum and minimum resolution of 0.75 and 3 arc seconds for the 1:50 000, and 3 and 12 arc seconds for the 1:250 000 respectively, depending on latitude.

Place the .dem file in a folder under the USA DEM 24K path or the USA DEM 250K path set in OziExplorer3D configuration in OziExplorer.

The data can be downloaded from here http://www.geobase.ca/

A CDROM was produced which contains height data for all of France at 75meter grid spacing. This CDROM is no longer available for purchase. The height data on the CDROM is in Vistapro DEM format. For use in OziExplorer this data must be converted. A program is available here for download which converts this data to the Arcview BIL format.

Download the conversion program here Download the FranceVisualDem2BIL software This is a self extracting exe file.

A similar CDROM was produced with height data for the Alps, the conversion program has not been tested with this CDROM but should work ok.

Here is a link to a "plt2dem" program which makes a DEM file from OziExplorer Track and Waypoint files.

 http://gpspl.w.interia.pl/plt2dem/

(Author: Grzegorz Chyła)

The Data listed above is the data we are aware of, no doubt there are many other sources of data in other formats.

These are the formats that OziExplorer supports

It is our intention to support other formats where possible and also to support more map projections and coordinate grids. For us to support a particular format we would need a couple of example DEM files, information on the projection/grid used for the data and the specifications for the format of the dem file.

See the bottom of this page for details on making your own "default.ozproj" files.

The USA DEM 24K files are usually provided in the SDTS file format. OziExplorer does not read files in the SDTS format, these files can be converted to DEM using the sdts2dem.exe program provided with OziExplorer3D. The sdts2dem program was written by Sol Katz. A program called oziUnGzip.exe has been provided with OziExplorer3D which can uncompress the dem files and convert them automatically.

Height Data in XYZ format will not be supported as individual heights cannot be quickly read from files in this format.
 

Using Height Data Files by Specifying the Grid and Datum

Many countries supply Height data files (DEMs) which are projected in their own local grid and datum.

For many types of DEM formats it is not possible to store this information in the DEM file so it must be specified externally.

To do this OziExplorer uses a file called default.ozproj (a Projection file) which stores the Grid, the grid zone (if applicable) and the datum of the data in the DEM files in the folder.

This is an example of a default ozi projection file for using DEM's in other grids and datums.

• Download example file here - default_ozproj.zip

• The use of a default.ozproj file is optional

• If a default.ozproj is not found, the DEM is assumed to be using the default grid and datum for the type of DEM
   

•  see the table above, whether you will require a default.ozproj file for your DEM

The default.ozproj file is read as each folder is scanned, all the DEM files in the same folder are assumed to be using the parameters specified in the default.ozproj file. If you have DEM's which use different grids or datums then these must be put in their own folder with a default.ozproj file setup with the correct parameters. OziExplorer scans all sub-folders attached to the folder configured in Elevation Configuration so all the DEM's will be found.

Example Projection File

Below is an example of a default.ozproj file - this file is setup for the New Zealand Grid and Datum.

These are the lines in the file which control the DEM - not all these parameters are required in every instance, the parameters which are not required can be left out of the file. Read the instructions contained in the example default.ozproj file below.

• grid - the grid the dem is using

• datum - the datum the dem is using

• zone - the zone the dem is using

• delta_x - used to offset the height data in the x direction (east - west)

• delta_y - used to offset the height data in the y direction (north - south)

These lines are only needed for certain grids and projections

• lat_origin

• lon_origin

• lat1

• lat2

• k

• false_easting

• false_northing

Example default.ozproj file