Maps and Overlays

[Tony Anders]

I am wondering if this idea I have will work so I can overlay a map I have on to a topo map I have.

I have several maps of caves in my area. I have also started a process of varifying GPS Coordinates of these caves.

What I am wanting to try is use some transparancy printouts to overlay the cave maps onto a topo program to see where other cave entrances or exits may be at on the map itself. This will also let me know if possible new cracks and holes I find might as well be part of the already mapped system.

Has anyone on here ever tried to overlay the transparancy printouts on a map. I have version of National Geographic USGS topo maps for Kentuck, and I was wondering how to make the scale match the scale I have of the map.

I was hoping that someone else might have had this idea before so I could see if this will work. I guess I will just use two pieces of paper before wasting transparancies, until I get the scale correct. Well, at least close to being correct.

Thanks again for all the help.

[Brian Roebuck]

Tony,
This may be possible on your computer as well. I asume you use a Windows PC (I'm on a Mac). Some of the topo maps are available from the governemnt in digital form and you could scale an image of your map to match the topo map you choose. Programs like photoshop and paint shop pro can be used to set the background color of your map to transparent so that you really can overlay them onto a digital topo.

I suspect you could cheat a bit and grab a screendump of your topo map while looking at google earth, topozone, or any other one of those free internet viewers. It is easy to do. Just zoom in to the topo area you need, write down the scale of the map (changes with zoom-ins etc) and then press the "Shift" and "Prt Scrn" buttons at the same time. Open a program like MS Paint, Photoshop, etc and hit edit and paste. You will have an image of your whole monitor screen that you can save as a .bmp or .jpg type image file. You can crop out the stuff you don't need and save just the topo map part if you like. Then get your cave map, scan it in, adjust the scale to the same value as your topo image, use photoshop etc to make the background transparent, and then using a program that can add layers to existing images (photshop and Paint Shop Pro can do this) put it on top of your topo image in the correct position. Now "flatten the layers" and save the final image as a single layer image with the map showing up on the topo all in the same scale.

All of this is not super easy but it is not too bad if you have the software. Optionally you can crop your topo image and print it out and make a transparency of your cave map. The computer can help you scale your topo printout image to match your map if you try various software to increase or decrease the size of your image. If you increase the image you may lose some detail though.

Hope this gives you a few ideas.

[Tony Anders]

Thanks Dr. Beaner.

I was familiar with how to screen capture...(shift print screen) but I didn't know the other stuff you told me, I will try that. I think you know what I am trying to get at by doing this. Like yesterday we found a new crack on the exterior of a cave we know is in a mountain there. This will tell me about where the crack or opening is if it is indeed close to the mapped portions of the cave.

Thanks again, I will try the MS paint and photoshop.

Do you have any place to download a free program like MS paint or Photo shop. I may have it, but I don't think I do...


Thanks a bunch.

[Brian Roebuck]

MS (Microsoft) Paint is included with all version of Windows found at: Start/programs/accessories/paint. Photoshop and Paint Shop Pro (PSP) are not free software. You can find them and download them illegally but I don't recommend that.

There is a free program called the GIMP (Graphic IMage Manipulation Program) that will do what you need and can replace Photoshop or PSP. It is not easy to use but has all the power you need to do the job. There are lots of tutorials and FAQs on how to use it though so you should be able to search around and figure it out.

Go here to checkout the GIMP:
www.gimp.org/windows/ where you can find the basic FAQs and other info.

Go here to download the easy install for Windows files:
gimp-win.sourceforge.net/stable.html

I noticed there are also FAQs and other stuff you may find useful there as well.

Enjoy it!

[Azurerana]

7.5 minute topo overlays are usually done at 2000 ft to the inch.

All you have to do is adjust your cave map to the same scale. This can easily be done on a xerox machine or with a scanner, which has enlarge/reduce capability. Any enlargement/reduction you do with non-GIS pegged images (bmps, jpegs, etc., as opposed to arc files. drgs, etc.) is going to have some 'splay' along the edges-- it is the fact that these are not GIS pegged (point A on map A correlates to point B on map B) and the fact that scaling (even digital scaling) introduces error into the image. This is why paste-together maps often don't line up on things like roads or such. You need 3 non-linear points to make a good correlation.

You can make transparencies on your computer printer, or on a xerox. These can be crudely GIS pegged by using 3 GPS readings (in a triangle) taken at the cave. One at the entrance, and one each on the ground but off to the sides of the axis of the main cave passage and oh, 500 feet on a diagonal from the entrance. Correlate those GPS locations to your topo map at the same scale.
Make sure your GPS is on the same datum as the map-- NAD 27 or NAD 83 or WGS 84.

You likely can do the same thing in the programs Dr. Beaner suggests, but if you're really into this, try to find a copy of ArcView or ArcGIS, or some other GIS program. It is much easier in those programs.

Have fun! I've done a bunch of this. I found just using a reducing xerox and sheets of paper and a lightbox easier to do than try to do it inside a computer, except when I had access to GIS. then, it's a snap.

[Brian Roebuck]

Azurerana,
There is a free GIS program for many platforms (Windows, Linux, Mac OS X etc) called ArcExplorer. I have never used GIS software but have it installed on my Mac. I'll have to try it out for overlaying maps on topos etc.

Go here for the Windows version:
www.esri.com/software/arcexplorer/about/arcexplorer9.html

and here for a Mac OS X compaitble version:
www.esri.com/software/arcexplorer/about/arcexplorer-education.html

This could make things too easy if it can do all this in one program.

Thanks! ;D

[Azurerana]

I've got Arc Explorer. It is very good for viewing GIS files, and some really simple manipulations of files in ARC format or which were already shapefiles. I'm not sure that it can do the actual georeferencing between layers, though. I'm not a GIS expert--had a one semester class in it, and had to do projects georeferencing original data. I always had to truck over to the computer lab to use the school's ArcGIS in order to overlay my datapoints on the standard USGS digital raster graphic (DRG), though.