Merging numerous GPS log files

Dan Robinson

Staff member
Jan 14, 2011
St. Louis
The recent chase range thread had me thinking about how to do a mass merge of all of my GPS logfiles. I have been using GPS Visualizer for mapping out my logs for several years, and it works great, though it limits you to merging only 3 files at a time and there is a size limit per file. You can manually merge the files yourself using spreadsheets and/or text editors, though after about ten days' worth of data, the files get pretty cumbersome to manage even with a powerful computer.

I have a few hundred GPS log files going back to 2004. Ideally I'd want to have something that only takes a sample of GPS points from those files, maybe every 100th or even 1000th point from those files just to show a broad overview of each chase day. Parsing the full logfiles for all of those days is going to be prohibitive no matter how it's done, I was hoping there was some utility out there that could manage it. Any ideas?
Mar 2, 2004
Wichita, KS
I will second this question... unfortunately I am not on my home computer which has links to some of the sites I use, mainly to convert Delorme into files I can put into Google Maps or similar software, but the idea of merging years worth of data has crossed my mind and like Dan, kinda got tipped off to this even more so in the recent chase range thread. So anyone here who could point in a good direction would make at least two of us very happy and probably pretty nerdy :D
May 25, 2012
Albuquerque, NM
Unfortunately I'm not going to be too helpful here (in terms of a off-the-shelf answer). My process has never really needed to be that scalable, so it's embarrassingly manual. I end up with a KML file for each chase year, and each chase day is a separate LineString object within the KML which stores the GPS coordinates.

Step 1: take my GPS logs (often just SN data pulled from their site) and use that to create a turn-by-turn directions in Google My Maps (heavy use of the "additional location" ability to get all the chase locales mapped in)
Step 2: Save/Export that map to KML
Step 3: Copy the GPS coordinates from KML into Excel, keep every 10th row (good balance of file size and route precision). Copy back into KML.
Step 4: Merge KML into "Season 20xx" KML file for the season. Use that on my website.

Are your Delorme or other GPS files human readable? If so it seems like a pretty simple custom script / parser program could be written to open each file, grab every xth coordinate, format in KML, and write the header/footer data to a new KML file.

Mark Blue

Staff member
Feb 19, 2007
I recently posted that Notepad ++ might work but then I deleted it because I wasn’t sure if my suggestion was viable. Today I found this on Stack Exchange Bulk edit and merge KML files where you can use that and another Python library to finish the job using pyKML found here Welcome to pyKML — pyKML v0.1.0 documentation. See the only answer in the question string and hopefully it’ll help. I’ve never done it myself but it sounds doable with a little trial and error and determination.