Exploring the world of free tools for GIS, GPS, Google Earth, neogeography, and more.
It’s nothing fancy, but Zonum’s GPXViewer website lets you upload a GPX file (points and tracks), and then quickly plots it in a Google Maps interface:
No editing, export or additional info in this app, just display; but Zonums has other web apps like Digipoint and MapTool for that.
Art writes about his programs Garmin 60CSx Whiz, Garmin Colorado Whiz and Garmin Oregon Whiz, which modify the firmware on a Garmin GPSMap unit to display a custom startup image and other alternate graphics. 60CSx-supported units include:
The interface looks straightforward enough (graphics from the program website):
 |
 |
 |
Sample graphic images are provided for the 60CSx whiz, but you can also use your own (love the kookaburra):
And apparently they do what they’re supposed to:
I say “apparently” because I’m too chicken to try it out, even though Art has a pretty solid hack programming resume. But if any braver souls want to give it a try and post their results in the comment section, have at it!
I’m not a .Net programmer (I’m still stuck in the primordial ooze that is VB6), but if you are, you might want to check out GMap.Net, a free and open source .Net control for embedding online map services in Windows applications. You have the option of displaying maps from Google, Yahoo, OpenStreetMap, Bing or ArcGIS, with tile cacheing an option for faster performance. Several demo apps are available to show what you can do:
One quick tip: right-click and drag to pan the map (took me a while to figure that one out).
GetLatLon pretty much does exactly what its name implies – gives you the latitude/longitude of a point in a Google Maps interface. A crosshair at the center of the display marks the position for which coordinates are given at the bottom:
Digipoint can perform the same function, plus many more, but if all you need is a coordinate position, GetLatLon has a stripped-down simplicity that makes it easier to use. Just keep in mind that coordinate positions in Google Maps can be tens of meters off from the true position (see here and here).
As a demo of the ArcGIS API for Flex, ESRI has a new page that lets you create an embeddable/shareable map of demographic data by US county. Only seven datasets available now:
Map creation is trivially easy – select the demographic dataset from a dropdown, zoom the map to the desired extents, set a map size in pixels, and you’re done; links to a map with your parameters, and code for an embeddable map, are generated automatically. Here’s an embedded map, scrollable and zoomable; unemployment rate is the defaultdataset, but you can choose other sets with the dropdown menu at upper right:
More datasets would be nice, as would control over colors and ranges …
The huge number of online support resources for Garmin handheld GPS units dwarfs the number of comparable sites for info and data for the Magellan Triton GPS line. Still, there are a few very useful sites to bookmark if you own this raster-compatible GPS unit.
If you want to use a raster map image in a GIS program, it needs to be calibrated so that the software will know the geographic position of every pixel in the image. This calibration data can be embedded in the file, as in GeoTiffs and MRSID files, or external as in worldfiles. If you have a raster map image which doesn’t include this calibration data, you’ll need to create it yourself; this process is called “image registration” or georeferencing. There’s a number of free programs that can perform this function, and I’ve put together a list of some of them below; if you know of others, please let me know and I’ll add them. And if I’ve included a program that doesn’t do georeferencing (very possible, since I haven’t used all of them), let me know that as well and I’ll drop it from the list.
One thing to keep in mind: some of the programs only work correctly if the map image is already in a specific map projection like UTM or geographic, and you use the same coordinate system to georeference the image. As a general practice, it’s always best to use the same coordinate system the map was created in to georeference it. For example, if you have a map in the UTM projection, and use geographic coordinates to georeference it, the resulting calibration is unlikely to be accurate over the entire map (unless you’re at the equator). Some programs let you warp the map image to get it to match the coordinate system, a process known as “rubber-sheeting”; this is especially useful for those maps that aren’t drawn accurately, like old or hand-drawn maps, or maps created in no-longer-used coordinate systems.
BTW, I haven’t used most of these for georeferencing – GlobalMapper is my program of choice for this function. It’s not free, or even cheap, but it works great for georeferencing, including rubber sheeting. For beginners, I’d suggest looking at MapWindow, qGIS or MicroDEM first before going on to the more advanced software.
MicroMSI (link may be dead)
Online map rectification tools
Yesterday’s post was about a site that categorized biomes with very fine divisions based on vegetation, soil moisture, surface lithology, etc., all with the underlying concept that for most areas this was a representation of an actual natural biome. The creators of the concept of anthropogenic biomes go in a different direction; they believe that the impact of man upon the natural landscape has been so profound, with only about 11% of the earth’s surface still truly6 wild, that most of the biomes of the world must be described by at least partially including the effects of mankind. They’ve broken down biomes into just 21 categories:
And created a world map using these categories:
You can download a PDF of the above image, an ArcGrid file for use in ArcGIS, or a KML file for viewing in Google Earth on this page. Viewed in Google Earth:
Also available are map viewers for this data in Google Maps and Virtual Earth (latter didn’t work on Firefox for me).
You can watch a Discovery Channel video on the concept of anthropogenic biomes here.
