Terrain2STL

A web-based service that converts publicly available HGT files to useful STL files.

Try it Out!

This project is running on a Google Compute Engine server at jthatch.com. It's updated soon after any commit to this repository.

You can also download everything here and start the server with:

node terrainServer.js

It will run at localhost:8080.

To run without static file serving (only needed if you're using another static file server such as NGINX), start with static serving disable:

NOSTATIC=true node terrainServer.js

A few .HGT files are included, but not the whole set. You can get the rest from the USGS, or I could send you few.

Install

Build the STL generator program with a simple make:

you@comp:~/.../Terrain2STL$ make

If that's successful, generate a test STL with

./celevstl 44.1928 -69.0851 40 40 1.7 0 1 3 1 test.stl

and you should be treated with a model of scenic Rockport harbor!

The arguments here are:

• Northwest corner latitude
• Northwest corner longitude
• Model width ("pixels")
• Model height ("pixels")
• Vertical scaling factor
• Rotation angle (degrees)
• Water drop (mm) (how much the ocean should be lowered in models)
• Base height (mm) (how much extra height to add to the base of model)
• Step size (hgt cells per model pixel)
• Output file name

Web Interface

To run the web interface to Terrain2STL, you'll need Nodejs. With that installed, first run install all the necessary node packages with

you@comp:~/.../Terrain2STL$ npm install

Once all the packages are install, start up the server with

you@comp:~/.../Terrain2STL$ node terrainServer.js

and the website should be up localhost:8080/!

To get the Google Maps view to load, you'll need to get a (free) Google Maps API key - see here. Once you have your key, copy example.include-maps.js to include-maps.js and replace the GOOGLE_API_KEY string with your own API key.

To-Do List

• Add a resolution slider Box size is in multiples of 120, so allowable downscales are 2,3,4,5,6,8,.. Actually DEM resolution is 1/3, allowable downscales are 2,4,5,8 Probably 1/8 resolution is minimum desirable
• Draw the northern and southern boundaries of the data set
• Add a negative version for molds
• Make a manifold surface option (bigger file, but better performance)

Descriptions of Files

• /hgt_files

  • This directory contains some sample HGT files for testing. Included are Mt. Everest; Rockport, Maine; and San Franciso Bay.
  • The whole dataset is 40GB, so only a few files are included.
  • This could also be a made a symbolic link to another directory that contains your collection of HGT files

• /src

  • This is the source code for the part of the program that actually creates the STL files

  • /src/elevstl.c - STL-creation program. Accept command line arguments

• terrain2stl-proto.html

  • The prototype for the HTML source of the website. Must be edited to contain API keys.

• terrainServer.js

  • Node.js server. Takes parameters from the HTML page and passes them to elevstl to create the STL.
  • Also handles client downloading of pages and files.

Done

(Previously on to-do list)

• Make dataset voids not just a fixed negative value.
• Make models watertight.
  • Fix voids in edges of models
• Increase maximum box size.
• Fill voids in dataset.
• Make the 3 arcsecond resolution available in all sizes.
• Add ability to cross tiles. !!!
• Make Print and Download buttons disappear or defocus when the selection box is moved
• Make the selection box reflect changes in the Lat/Long boxes
• Decide on a maximum file size
• Add longitude compensation to correct for the distortion caused by the Mercator Projection
• Normalize model height to remove vertical offset
• Change view to fit lat/long
• Vertical scale slider
  • Increase scale range (maybe to 4x)
• Compress STL files