I have a dataset that describes a few million incidents along Texas roadways. The vast majority of incidents only list a highway name and a milepost. For example, milepost 120 on I-20 or milepost 263 on US 60.
How would I convert these milepost/highways to latitude and longitude?
This is for a low-budget academic project, so trying to stick with free tools as much as possible.
My Google searching hasn't turned up much fruit, although some indications are that TxDOT may have data I could request through the Texas Public Information Act, but not sure yet.
Answer
I'd try to contact Michael Chamberlain at TxDOT. He's made a lot of progress in opening up TxDOT data, for example this map viewer. His contact info is at the end of this presentation.
I suspect you might need the TRM Data Export, as described here.
If you have a table of points with: HighwayName Latitude Longitude Mile
Then it is a matter of interpolating lat/long between two adjacent rows using the Mile post value (safe to assume flat earth here). If you have historic data, keep in mind road re-alignments can sometimes result in milepoint changes. I think TxDOT tried to manage this using a method described in this paper, but was unsuccessful.
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