TransDEM Forum

I have a 64 mile route to develop,its the Uintah railway on colorado . its a generally a narrow route running north to south, but there are some branch lines that necessitate some longer east west developments.
I've read Roland's tutorial for google earth and also Hi-ballers tutorial.
I found that using Hiballers guide of moving south and east diagonally then led me to some points where images were overlapping a large amount and was wondering if this would cause me some issues when i go to assemble the map in transdem.
I would find it more logical to just work across the map from east to west , then drop down to the next line of images and so forth . if I did this , is this unworkable? if i did do this, is there a particular direction that works better then the other ?
Also, the sheer size of this route is going to generate hundreds of images, would it be better to divide the route into sections and then merge each module later on in trainz?
finally just how much overlap is needed for each image to work with the other tiles ?

The screenshot/placemark method for Google Earth should be seen as a beginner's option to incorporate ortho-imagery. It's straightforward and easy to understand. Nonetheless, it's only a partly automated approach with a couple of manual steps still required. Since this method is a picture by picture procedure and all images are independent of each other, you can work in any order you wish, without a penalty. The only restriction is the crossing of a UTM zone border, every 6 degrees longitude (i.e. east/west direction). But this applies to all geo data sources, not Google Earth alone. And UTM border crossing can also be dealt with, TransDEM has functions for it. However, unless you actually encounter two UTM zones in your project, I wouldn't bother.

Now, TransDEM also offers a second option to use ortho-imagery: Map Tiles. This is a much more automated way of doing things. At first glance, Map Tiles appear to be for cartography only, but we also can use the technology for aerial images. Map Tile usage requires a one-time set-up, but after that, it's much more efficient to use.

To familiarize yourself with Map Tiles, do tutorial #7 in the TransDEM main manual. Then check out Microsoft Bing (Virtual Earth) ortho-images. If they provide what you need, stick with them. If you think you still prefer Google, you have to create a Google Maps API key: http://forum.transdem.de/viewtopic.php?f=6&t=465. That's because Google retired anonymous access to Map Tiles last year. Once you have your Google Maps key and registered it in TransDEM, you can then access the very same ortho-imagery you see in Google Earth.

You will find that the special feature: "Map tiles along a path" will help a lot. It allows to split the number of images into separate paths, e.g. one for each branch line, and also will handle most of the overlap for you.

Since ortho-images usually go to UTM tiles in your Trainz route you can work in stages. Load your images you acquired along your paths one by one and run the UTM tile export for each path, with the vector path also open, as it will serve as a UTM tile creation filter.

Note: We have "map tiles" and "UTM tiles", two different concepts with two different purposes, one for acquiring raster-type geo data, the other to get higher resolution textures into your route. Nonetheless, the two have a few things they can share, like the vector path.