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Ask HN: How do I make my own map?

5 points by gorgoiler ↗ HN
My neighbours and I share a community park that needs surveying. I have been volunteered and am hoping it will be possible with a simple theodolite and free software. If you’ve done your own site survey from scratch, what tools, software and HOWTOs helped you the most?

7 comments

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slater
leaflet.js?

https://leafletjs.com/

gorgoiler
Seems to be for rendering? I’m talking about getting my boots on the ground and measuring where things actually are!
bigiain
How big is the park? And what sort of accuracy are you after? What equipment do you have available and/or what sort ofd budget are you hoping to keep within?

For an "on the cheap, lots of DIY" approach - I've got an inexpensive (~$40 from memory) laser rangefinder with sub cm accuracy and a range of a bit over 100m (it'll get ~120m for things with "good" reflective properties, sometimes only 50m or so for "bad" surfaces). If the park is a suitable size, you could probably start with a Google Satellite view, and measure enough distances to triangulate everything to calibrate the satellite imagery. I've considered (but never gotten around to) attaching a 3 axis digital compass module so I can record angles and elevations for each distance measurement. That'd help a lot of there are lots of objects you want to plot positions for - you wouldn't need 2-3 measurements from different known locations for each object that way.

See also my other comment about using a drone and photogrammetry.

gorgoiler
Great questions, thank you for you responding.

It is a small park, 600ft square, but conservation means we would like to map tree locations precisely. Half a trunk diameter would do: around about 6”.

In metric that’s around 200m with accuracy of 200mm.

Budget is up to $500. We have time and tech ability on our side, so don’t need a Total Station (something I’ve learned about recently) that can do everything, but it would be nice.

arthur2e5
The more amateur world I am familiar with (OSM et al) does not go for a theodolite at all. The general approach is to satellite-trace the place out and use GPS tracks for what it can’t cover.[1] For more detailed shapes or up-to-date imagery, OpenDroneMap might be used to assemble own drone imagery.

  [1] https://wiki.openstreetmap.org/wiki/Mapping_techniques
The rendering part is usually done by leaflet on the web. GIS software should allow importing from OSM too.
bigiain
Using inexpensive drones and photogrammetry to stitch lots of photos together is fairly straightforward these days:

https://www.mobiddiction.com.au/drone-mapping-in-4-steps/

Depends a lot on what you mean by "site survey" though.

The photogrammetry used there also created a depth map from the stereography where images overlap:

https://www.mobiddiction.com.au/wp-content/uploads/2019/11/T...

You can see in the bottom right corner of that the elevation changes for the roundabout and the ~120mm high curbs at the edges of the roads - and the gradual slope of the whole site towards the top right corner. (There's a lot more detail and calibration data than that image shows in the full data set there.)