Mapping Tools
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There are a small number of map and image making tools that I offer on this page.  The first is a tool which allows you to remap images as backgrounds for geostationary weather satellite data, the second is related to my WXtrack program, and allows you to make a customised master overlay, and the third is a set of programs for using some public data sources.  I conclude with a note on data sources.

MapToGeo - for GeoSatSignal

MapToGeo allows you to take images in Plate-Carreé projection (azimuthal equidistant - linear latitude and longitude) and convert them into the view as seen by the current geostationary weather satellites around the world.  This allows you to use the images as attractive backgrounds for GeoSatSignal, combining an idealised daylight image with the current cloud patterns, as an aid to weather presentation.  This technique was suggested by Ferdinand Valk.  The great thing is that images like the one below can be generated day or night - there is no need to have a daylight image for the region.  This greatly extends the ability of GeoSatSignal to produce easily understood data right round the clock.

What the users say:

  • "Finally a tool that allows me to bring a uniform view to presentations of world wide weather, irrespective the Geostationary satellite used and time of day.  Simple, functional and easy to use." - Ferdinand Valk, Earth at Large.

  Download MapToGeo
  Register MapToGeo

Here are some sample results from GeoSatSignal using a background (from Blue Marble) converted with MapToGeo.  Many thanks to Ferdinand Valk for providing these sample images.  He can be contacted for large format images like these with a superb print quality, and you can see Ferdinand's own comments about the program here.

Cloud data from the Meteosat-8 weather satellite overlaid on a remapped background from a Blue Marble image.  This data was from the 1800 UTC scan when much of Europe was in night time, yet the image looks like a daylight one!
(Processed by Ferdinand Valk)
Cloud data from the GOES-12 weather satellite overlaid on a remapped background from a Blue Marble image.  The palette used can be tuned for best match to the weather expected in a particular season.
(Processed by Ferdinand Valk)


Image sizes

You may find images of various sizes on the Web.  There are limits to the size of images that MapToGeo can handle directly, but images up to 5400 pixels wide (east-west) and 2700 pixels high (north-south) should work in the program without problems.  For generating the larger output formats, you will probably want to have at least 1 GB of memory in your PC.  

To alleviate the image size problem, V1.0.2 of MapToGeo provides the option to use an input image which is only a fraction of the full Plate-Carreé projection, and combine the resulting output geostationary projection images in your favourite image editor (e.g. by arithmetic and taking the lighter image, or by using layers).  There are three options for input image size:

  • Full-size image, up to say 5400 x 2700 pixels, 15 pixels per degree.
  • Two half-size images, one for the western hemisphere (-180° to 0° longitude) and one for the eastern hemisphere (0° to +180° longitude).  Each image should be square, and sizes of up to 10800 x 10800 pixels per image have been tested (60 pixels per degree).
  • Four quadrants - western hemisphere north, western hemisphere south, eastern hemisphere north, eastern hemisphere south) each with a 2:1 aspect ratio.  Images with a size of 10800 longitude and 5400 pixels latitude (60 pixels per degree) have been tested.  These are referred to like the GMS-5/MTSAT-1R weather satellite quadrants:
    • A is north-west
    • B is north east
    • C is south-west
    • D is south east

The quoted sizes are not maxima, and you may be able to go a little larger, but perhaps not twice as large.


Download MapToGeo

V2.0.2 Add 9.5° East HRV segment (Europe & wide), add GOMS-1 support, hide obsolete mappings - but add option to show them if required (File|Options menu), accept PNG for input and allow for batch mode output, program will try to use 3 GB memory if needed (but doesn't support Windows Vista), command-line mode for remapping Meteosat full-scan data to rapid-scan segment.
V2.0.4 Add Himawari-8 segment, add 41.5° East MSG IODC segments (full disk channels 1-12).

If you don't already have a MapToGeo 2  key, contact me for a fresh licence key before using this software.
  • Download MapToGeo V2.0.4 (1,054,829 bytes;  2016-Sep-27)
  • MD5 checksum: E84133796BD33D155A14595F274E1E93
  • Register MapToGeo
  • If you don't already have it, download the runtime Library Bundle which contains support routines for MapToGeo.  (Do this if you get messages about missing DLLs when you try and run the program).
  • Gérard F6BEK has kindly donated this zipped MS Word document (in French) about using MapToGeo.  Merçi beaucoup, Gérard.
  • Visit the SatSignal self-help group to discuss this software with other users.

Beta version: This program is under continual development - check here for the latest update.

MakeOverlay - for WXtrack

This program will allow you to create a customised master bitmap image for using overlays with WXtrack and SatSignal. You can customise the grid-line spacing, whether a numerical annotation is displayed and its font, and whether or not the grid-lines should overlay countries. You should already have a working version of WXtrack, and the countries.dat file installed.

     Download MakeOverlay V1.4.0, 34436 bytes, revised 2002 Apr 04

If you do not already have the file countries.dat, you can download here.  You will need to unzip the archive and extract the countries.dat file to appropriate location.  Note that more recent versions of countries.dat include a few extra islands.  If these appear to be missing from your version, check that you only have a recent copy, and not an old version in another folder.  V1.4.0 allow the suppression of both grid lines and country boundaries.

Note that you will require a graphics driver that can handle more than the full resolution of the screen.  This is usually true with Windows NT drivers, but may not be true with some Windows 9X graphics drivers.


LonLat2dat - updating Countries.dat


This small package contains a program to convert MapGen format (perhaps downloaded from the NGDC Coastlines Extractor) data into a format you can append to the Countries.dat file.  Please note that this package is not supported by me, but self-help is available in the SatSignal self-help group.  There are full instructions about updating Countries.dat in the Zip download.


GPS Radio Horizon Plotter

Unsupported program which uses the signal strengths of GPS satellites (as reported by your GPS receiver) to determine your radio horizon.  One side result is a polar plot of GPS satellite coverage, showing the hole in the coverage at the pole (as the satellites don't orbit that far north).

Download Download the GPS Horizon plotter

Requires my runtime Library Bundle to run

Writing to the timekeepers mailing list, Jan Hoevers explains: GPS satellites are not geostationary.  The instructions that came with your receiver recommend "clear view of the sky".  Unless you live in the middle of a desert a clear view of the entire sky will be impossible.  Luckily you won't need that, because - no matter where on earth you live - a large part of the sky will never show any GPS satellites.  You can make clever use of this when you have to position the antenna in a suboptimal position, e.g. on a window.

The orbital plane of any GPS satellite has an angle of 55 degrees with the equatorial plane, taking the satellite up and down between 55 deg north and 55 deg south.  The satellite constellation populates a band - more or less donut shaped - around the earth, centred around the equatorial plane.  No GPS satellite ever flies over the poles (some other satellites do).

Seen from the earth's surface that leaves a large circular area of the sky - cantered over the pole - where no satellites fly.  In tropical and temperate zones part of that circle is below the horizon, at latitudes of more than 55 deg the entire circle is above the horizon, and a (small) part of the "opposite side of the donut" becomes visible at the northern horizon (southern horizon if you're down under).

Close to the poles the satellites will appear to remain close to the horizon, with the unpopulated circle overhead, while near the equator two unpopulated circles are visible, north and south, making the satellites appear in a band from east to west.

Myself I live at a latitude of 52 deg north, meaning the northern sky is not interesting (except for a small band of 3 deg through the zenith).  Consequently I have my receiver glued to the outside of a south looking window. A position on the roof would be possible, but I won't go through the trouble, because no improvement can be expected.

Try to imagine where the satellites fly as seen from your position, it will help in finding the best position for your GPS antenna!


Other Mapping Tools

A few people have asked about the data and programs used to create the hill-shaded topographic map.  Data came from GTOPO30 for topography, and GSHHS for shoreline and lake data, and I wrote my own programs to manipulate this data.  You can download a 197 kB package containing pointers to the data, and the Delphi 5 source code that I used if you wish.  This is really just for your interest, and is informal and not subject to any version control.  Last updated, 2002 Mar 17.  You will likely need a few other units if you want to recompile the programs, but they would be easy to modify to suit your own purposes.  Please contact me if you have any notes or programs you might wish to add to this package.

    Download the Mapping Tools package

Programs in the package

All these programs come with Borland's Delphi 5 source code ready for you to compile and use.  You may need some of my other units from my Components page.

  • GSHHS reader - simple test program to read GSHHS data.
  • GTOPO30 to Height Image - program to subsample heights into an image for storage.  Uses GSHHS lake data to add lakes and inland seas to the GTOPO30 data.
  • Shade Height Image - program to covert a stored height image to colour, derive a shading function from the rate of change of height, and make a combined hill-shaded image.
  • ETOPO5 - program to demonstrate reading the lower-resolution ETOPO5 5 minute elevation data and the COUNTRIES.dat country and state boundary data.  This program can now also read the 2-minute data TOPO_8.2.img.


Some fun stuff


Data Sources


Blue Marble comprises a set of clear-sky earth images at various resolutions.  Can be used with my MapToGeo program.

NASA's Earth Observatory writes: "Everyone knows that NASA studies space; fewer people know that NASA also studies Earth. Since the agency’s creation almost 50 years ago, NASA has been a world leader in space-based studies of our home planet. Our mission has always been to explore, to discover, and to understand the world in which we live from the unique vantage point of space, and to share our newly gained perspectives with the public. That spirit of sharing remains true today as NASA operates 18 of the most advanced Earth-observing satellites ever built, helping scientists make some of the most detailed observations ever made of our world.
"In celebration of the deployment of its Earth Observing System, NASA is pleased to share the newest in its series of stunning Earth images, affectionately named the “Blue Marble.” This new Earth imagery enhances the Blue Marble legacy by providing a detailed look at an entire year in the life of our planet. In sharing these Blue Marble images, NASA hopes the public will join with the agency in its continuing exploration of our world from the unique perspective of space."

The monthly global images may be found here - click on the image below to get a page of downloads!

February 2004


U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, 2006. 2-minute Gridded Global Relief Data (ETOPO2v2).  This data is approximately 2km resolution at the equator, and has 1 metre height resolution.  

The compressed raw data is about 72MB, and can be downloaded in both big-endian and little-endian versions.

Les Hamilton kindly provided this example of using ETOPO2 data.  The image has been JPEG compressed for reduced download time and storage space, and the original has much better quality.

Les Hamilton has also kindly provided a Delphi program to create maps like that above from the ETOPO2 data file.  You can download an installation package here:  Les is willing to make the Pascal/Delphi source code available, and if you are interested, you can make your request to Les here: lesw (dot) hamilton (at)


Digital heights of the world and sea floor level.  This is a single file of data at 5 minute intervals, making 360 x 12 points in longitude, and 180 x 12 points in latitude.  Note that the file formats are slightly different, Jones having one extra 16-bit word per line of data (longitude), and being in PC order (little-endian, or low byte first).

Les Hamilton writes: "For VB5/6 programmers interested in learning how to make use of the ETOPO5 elevation data, I have developed this small Visual Basic program.  You are free to download and modify it to suit your own map creation purposes.  All source code is included".

There is a two-minute resolution version of this file which has Mercator projection covering most of the world at the URL below.  It is about 136 MB uncompressed.


Digital heights of the world - at 30 second intervals.  This data is divided into 33 tiles - about 50 MB each, but a lot less when compressed with Zip.  You should be aware that the topography data occupies some 1.74 GB when expanded, but it is available at cost from the US source on CDs.  Sources:

and GMT

GSHHS is shoreline and lake data that comes at a variety of resolutions.  You will probably find the low resolution data (5Km, 1.1MB) adequate, there are also intermediate resolution (1 km, 5 MB) and high resolution data (0.2 km) available.  Its main use here is in adding lakes to the height data, which otherwise only has major seas.  

If you need to resample to a different accuracy (I find about 2.2 km about right for HRPT data), there is a C program provided in the GSHHS archive which uses the Douglas-Peucker algorithm.  Just in case you don't have a C compiler to hand, I have provided a ready-compiled version.  Updated 2006 April 20 for the V1.3 GSHHS data - ready-compiled software V1.5 for V1.3 data.

I use the raw GSHHS data myself, although the authors offer a very fine map generation package called Generic Mapping Tools (GMT) which has a compiled version of the data.


Here you can get some land-sea mask data.  Please see here for a full description:  

I've provided a local download which is zipped to save you time and bandwidth.  

Copyright © David Taylor, Edinburgh   Last modified: 2019 Apr 18 at 11:44