How to query DEM elevation values in a web application based on cursor/click point location?

Question

I work for a city government that has LiDAR derived DEM rasters which we would like to make accessible to other departments in the city. The problem is that many departments don't have anyone with GIS skills and/or licenses. We are looking to develop a simple, easy to use application that will just return elevation values from the DEM based on cursor click/point location. We would like to do this without having to serve out the high resolution DEM dataset for speed and ease of use of the application.

We currently have GeoPDFs that can return elevation data as long as users have the TerraGo toolbar installed. This is expensive and extremely cost-prohibitive so we are looking for a cheap option that can be used by employees and the public alike. We are just looking to query based on XY location of a point which will return the elevation value based off of the DEM. Has anyone done this or have advice on the best way to proceed?

We do have access to Google Maps Engine (the Elevation API is SRTM so resolution isn't good enough for our purposes), as well as ArcGIS Online.

Also worth mention: We are currently running Oracle Spatial but are transferring to SQL Server 2012 with ESRI's LGIM for our spatial data(geodatabases and feature classes).

Answer 1

Put your rasters into a place where gdallocationinfo http://www.gdal.org/gdallocationinfo.html can access them. The files can be in a local filesystem but GDAL can read them also through http with the VSI system. Then make a light web application that captures the coordinates from your users, runs gdallocationinfo and sends the height value back to user. You hardly can do it cheaper.

This thread deals with a very similar case http://osgeo-org.1560.x6.nabble.com/gdal-dev-Fast-Pixel-Access-td5101243.html about serving DEM info from a mosaic of 55,501 DEM files from US.

Answer 2

You can use any web platform you'd like (particularly on Linux) because its very easy to query GDAL using "gdallocationinfo -valonly -geoloc /path/to/files/45w074.dem -73.123456 44.123456" and get the elevation you need. If you need higher resolution data the USGS NED 1/3 arc-second data covers 99.9% of the US now (it's 450 GB worth of IMG files, though).