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user453673


Mar
22
comment How to Create database using OGC compliant geometries and Custom type Geometries?
Similar question (not duplicate though): gis.stackexchange.com/questions/38863/…
Mar
21
comment How to Create database using OGC compliant geometries and Custom type Geometries?
From the title, I think he's asking about geometries which can be drawn on the screen and edited by the user at runtime and later stored as a layer of dynamic geometries, in a postgis database when the application's workspace is saved. Something like this would typically require control points and handles to be stored with the geometry, which isn't (as per my knowledge) supported directly by OGC. (at least I'd like to know) How would such dynamic data be stored in a database?
Feb
14
comment Most optimal algorithm for contour correctness?
Thanks. I've been trying to find out which algorithm GDAL uses for creating contours, but couldn't find any hint on that. Anyone here know? Basically my main requirement is that I should be able to use GDAL (or any other contour generation algo) to create reliable contours which are the best in terms of accuracy (when compared with any application that displays contours). I don't want to start using GDAL and then much later realize that it doesn't suit my needs of multicore support, accuracy, smoothening or specifying the height interval between major and minor contours.
Feb
13
comment Most optimal algorithm for contour correctness?
I agree. Good advice. But assuming the data constant, which would be the best algorithm/library, is what I'm asking?
Aug
31
comment Definitive source for downloading DEM data
Is there any website from which I can download at least a few GB of DEM data at once?
Dec
22
comment Differentiating a building from a road on a map?
Thanks for your answers, everyone. Steven?
Dec
10
comment What's an efficient way of detecting road junctions on a map?
Just sharing: Another database I've come across is this - <oracle.com/technetwork/database/berkeleydb/overview/…;. Apparently the queries are very fast because the queries are available as libraries which can be embedded in the application.
Dec
10
comment How do algorithms load pieces of maps?
@Brad: My answer is 'no' to all your questions :) I've edited my question; I guess I didn't ask my question clearly enough.
Dec
10
comment How do algorithms load pieces of maps?
@Dan: Edited. I've also answered my own question below based on something I found. I've heard the Hilbert curve is more 'optimised' than QuadTree (don't know how it's better optimised though). Besides, Berkeleys database seems a quick way of querying for tiles. Comments are welcome if you know about these methods of storage and access.
Dec
9
comment How do algorithms load pieces of maps?
Thanks, but I'm not working with tile images. Am working exclusively with the nodes of a road network. All my algorithm needs to know is which road-nodes are present in a certain region which I wish to load. My question is how these points will be stored (In C++) and recognized as squares or sections of the map. I'm sure there would be an efficient way to do it...
Dec
9
comment How do algorithms load pieces of maps?
I'm not working with tile images. The algorithm I'm writing deals purely with lat-long points. The 'pieces' of maps I'm loading are only sections containing road-networks and/or railroad networks (maybe vegetation boundary vectors much later). The road network within these sections will be processed by my algorithm. I'm sorry if I used the word 'tile' inappropriately. Maybe 'map-section-for-roads' would be more appropriate.
Dec
9
comment What's an efficient way of detecting road junctions on a map?
@Kirk: I'm a bit shocked at the situations you've mentioned. I'm new to GIS, and didn't even know that such possibilities existed. 1.Self intersection requires multiple segments. Unless it's a flyover, I would consider those intersections as junctions. 2. I'm not even able to visualize what degenerate geometry is, so I don't know what to answer. 3.Coinciding lines should be treated as two separate roads because that's how I assume they would be in real life too.