Tuesday, December 15, 2015

I Get By With A Little Help From My Friends

Talking to a friend the other day it occurred to me how fantastic it would be if Vr could import and display OpenStreetMap data.  Nothing fancy mind you but maybe create an image that you could use as a background for a quick check of the surrounding area or even flight prep.  Wow that sounds like a lot of work unless of course someone else has already done it.  One of the many beauties of Python is the number of fantastic libraries out there if you just spend a little time tracking them down.  If you take that a step farther and are willing to pass a little of the responsibility outside python using system calls or batch files the possibilities are nearly endless.  Let's just say I can now display an OpenStreetMap map image in Vr and it only took about 90 lines of python.  Here are a few of the major helpers besides the map site which is so worthy of support, contribution, and praise.

I know I have mentioned it before but I can't say enough about pyproj which I use to convert my local coordinates to geographic for sending out to various places.

Once I have the corners in Lat / Long the rest will be done by a batch file which is about the only thing my python script creates.  It could be done in other ways but I liked the idea of creating something that could stick around and be easily modified for use again.  So the batch file next makes a call to the openstreetmap.org API for grabbing the map data.

Once the OSM file is in house it will be converted to a bitmap using Maperitive.  I only use such a tiny fraction of the capabilities of this amazing program, but for my purposes using it's command line version with a custom generated script will fit the bill perfectly.

The original bitmap is created in Web Mercator and can also throw in a TFW and KML file for generic use or display by anybody if you want to send them along.  I however want to display it behind my map in a local coordinate system in whatever system I choose so the last step is to re-project the image using GDAL.

Is this the most advanced, professional, elegant way of doing it?  Of course not, you obviously don't know me very well.  As usual it is something you can hack together in just a short time with minimal duplication of effort that gets the job done.  Hooray for real programmers!!!

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For anyone interested in trying VrPython for the first time or if you are early in the game, I suggest going to the earliest posts and working forward. I use VrPython every day for many wonderful things, needless to say it will change and could potentially damage a file. Any risk associated with using VrPython or any code or scripts mentioned here lies solely with the end user.

The "Personal VrPython page" in the link section will contain many code examples and an organized table of contents to this blog in a fairly un-attractive (for now) form.