dchall81,008 post(s) |
We're having fun now! The USGS maps don't have street names, but that's not hard to figure out. It turns out they map pretty close to the current Bing and Google imagery, but not close enough for my OCD. There are four quads that cover what is now San Antonio. As it happens, the east and the west maps meet just about where I wanted to draw in the 1909 neighborhood, but again, not hard to figure that out. They all come in as polyconic projections as is stated on the maps themselves. Here's a picture of where the east and west maps meet. The red/yellow box/dot in the middle of the picture is the location where the corners of the two maps are supposed to meet, according to the notation on the maps. The location to the south is the NE corner of the SA West map as it imported. I suspect Tim would recognize this as a problem with the original projection. I'm not that clever with recognizing those things, plus I was looking for an excuse to use the georegistration tools, so that's what I did. As we say, there is more than one way to skin a cat...although there is probably a preferred way. At first I adjusted the lat/long locations as described in the video about georegistering the entire Earth. When that wasn't perfect, I used monuments on the ground, and that worked very well. At most I needed 5 points including four at the outer corners and one on the interior. These 1954 maps do align much better to today than the 1909 map did. I suspect the surveying equipment and skills had improved. In 1954 they used aerial surveys which were not available in 1909. Attachments: Errors in USGA San Antonio GeoTif Maps.jpg
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