Hi listers,
Perhaps others already knew this little trick, but I just stumbled upon it last week and didn't see anything in the archives mentioning it.
I found out that the Terraserver website has recent color images at .25 meter resolution for urban areas, one of which is my hometown of Portland, Oregon. I wanted to see if there was a way to automate the downloading of images by clicking on a mapper window, so I looked in the archives for some html code using MapBasic. What I want to do is click on a point and have the image and its world file saved nicely to my hard drive and then create a table automatically incorporating that info in order to register the image.
But I also discovered that I could actually use rectangles, lines, or even points for hotlinking to the Terraserver website and have the image pop up in a browser. Here's how I did it.
I made a small grid of rectangles, each 1000 meters square, in a CAD program and imported that to MapInfo in UTM coordinate system. I then used the following expression in the layer control -> hotlink dialog box and made it active for objects.
"http://terraserver.homeadvisor.msn.com/download.ashx?T=4&S=10&x="+Str$(Int(CentroidX(obj)/200)-2)+":"+Str$(Int(CentroidX(obj)/200)+2)+"&y="+Str$(Int(CentroidY(obj)/200)+2)+":"+Str$(Int(CentroidY(obj)/200)-2)+"&z=10"
In the mapbasic window I typed "Set Map CoordSys Earth Projection 8, 33, "m", -123, 0, 0.9996, 500000, 0" to set the proper coordsys.
Now, when I activate the hotlink lightning bolt from the toolbar and click in any rectangle in the mapper window, it will load my browser with a 1000 meter square image of that grid cell.
If I used a point table of say, dip and strikes instead, the geologist could click on a symbol and he/she would see the location of where they took the reading. It could be used for mine sites, parks, trailheads, telephone poles, or whatever can be shown with a point symbol, line, or a region. Just realize that it is taking the centroid x and y of the object to make the request to the Terraserver site, NOT the point on which you click.
Since the color images are only available for urban areas, you would need to get black and white images for other places. In that case, change the expression to read T=1.
If you are not UTM zone 10, then change the &z=10 to whatever zone you are.
The "+2" and "-2" are used to build a 5 by 5 grid of 200 meter images with the clicked point contained in the center box, so if you have a slower connection or don't want to download that large of an image, change them to something smaller.
If you don't want the resolution to be at 1 meter pixel size, you would need to change the &S=10 to the appropriate number and also recalculate the proper grid references. That's left up to the inquisitive folks to work out. :-)
Hope this is of some interest to someone.
Mark
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