Hi,
Here in France, National Geographic Institut offers elevation model as opendata. It consists in ASC (Ersi grid) with 1 point every 75m. Data covers whole country which represents 160 ASC files, each corresponding to a grid of 1000*1000 points => 160 millions points (= 1Go of ASC files)
I would like to create a plug-in (langage dev is C#) to pick a closed polyline in AutoCAD MAP, extract all points inside and generate a DTM.
I've thought of some solution:
1. keep ASC file, testing each grid to search intersection with my polygon, and for intersecting grids, test all point to keep whose inside.
2. transfer this ASC into database (SQLite, PostGis ...) and use API of geodatabase (point in polygon?) to extract points
3. use FDO API to extract point in polygon from Database
The other problem is ASC File use a Cordinate system covering whole country. According to my projects there are some other possible Cordinate system used which need transformation from my original data. If I use a database storage, is it more efficient to store this point in LatLong (WGS84) instead of any other CS.
The goal is to keep a execution time under 2 minutes.
If anyone have any experience in performance to manage such quantity of data and the more efficent way to access and transform this type of data.
Thanks
Olivier
