A technique for resampling raster data in which the value of each cell in an output raster is calculated using the value of the nearest cell in an input raster.

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7
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4answers
2k views

Calculate polygon field based on neigboring polygon attribute

I have a vector shape with many different sized polygons each possessing an own class name (for instance "houses", "houses with offices", etc ...) I want to assign a new field to each polygon ...
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vote
1answer
1k views

Finding nearest point in SpatiaLite without GEOS

I want to find the nearest point having latitude and longitude stored as Point in SpatiaLite. I read this and it has this example: SELECT feature_name, feature_class, ST_Distance(Geometry, ...
10
votes
2answers
2k views

Calculate Distance between a Polygon and a Point Along a Path

I am very new to ArcGis and am trying to figure out how to do this. Basically, this is what I am trying to do: I have a map of Canada and in it I have polygons representing areas (each about the ...
4
votes
1answer
287 views

Estimating cline width at multiple points along a trait gradient

In the map below I have 66 (green) points along the midpoint (0.5) for an allele frequency cline across the region (see map). I created the points by placing a point every 25 km along the 0.5 allele ...
20
votes
1answer
1k views

Nearest Neighbor problem in Postgis 2.0 using GIST Index (<-> function)

I'm trying to use Postgis 2.0 new function <-> (Geometry Distance Centroid) in order to calculate, for each row of my table (cosn1), the distance to the nearest polygon of the same class. I was ...
1
vote
1answer
448 views

Generate Near Table and keep all attributes

I am trying to calculate the angle and distance of points to surrounding polygons. The table is good and what I need but it doesn't maintain all records; the unique point and polygon IDs are not ...
13
votes
3answers
3k views

How does Nearest Neighbor Image Resampling work in ArcGIS?

I am trying to understand how nearest neighbor for the resampling of Image datasets works in ArcGIS. The output raster cell value is the value of the closest cell value in the input raster: In this ...
10
votes
1answer
496 views

How to efficiently find the closest point over the dateline?

I have a PostgreSQL 9.1 table with hundreds of thousands of PostGIS POINTs. For each of these I'd like to find the closest point in another table of POINTs. The points in the second table represent a ...
8
votes
3answers
5k views

How to find nearest neighbors between two tables with point locations in SpatiaLite?

I have started playing with SpatiaLite today and already stumbled upon a problem. For each point location stored in tableOne I would like to select one, nearest (linear distance) point from tableTwo. ...
12
votes
3answers
2k views

Optimize nearest neighbor query on 70 million point cloud on SQL Server 2008

I have about 75 million records in a SQL Server 2008 R2 Express database. Each is a lat long corresponding to some value. The table has geography column. I am trying to find one nearest neighbor for a ...
12
votes
3answers
3k views

Optimizing a nearest neighbor calculation using PostGIS

I'm using PostGIS to calculate the nearest neighbors of polygons. What I want to calculate is the minimum distance from each polygon, to the nearest polygon. Thus far I have got great help from Mike ...
6
votes
1answer
1k views

Nearest Neighbor calculation in PostGIS

I'm learning how to use PostGIS and spatial databases for analysis. What I am trying to do is perform a calculation to get the distance for the nearest polygon in a file, using the edge calculation, ...
7
votes
2answers
9k views

Find closest lat long to an input lat long (SQL Server 2008)

I have a point cloud in my database (SQL Server 2008 spatial). That is about 6 million records. There are 3 columns: id, value, geom. What is the optimal way of getting the 'value' at input lat long?? ...
7
votes
1answer
715 views

(Smooth) Isoline Extraction from TIN - Algorithms

Can anyone point me to a clear document or algorithm for extracting smooth isolines from a Triangular Irregular Network? I've seen some examples using the jagged linear methods, but can't seem to ...
14
votes
3answers
5k views

Algorithm to find nearest point

I've a list of a few hundred cities with their latitude/longitude. Given another location (also in lat/long) I need to find the nearest city. As I don't use any GIS, by now the obvious algorithm is ...
12
votes
6answers
856 views

PostGIS: Assign ID of point in layer A to closest point in Layer B

This should have been an obvious precursor (that I didn't ask) to my other question: PostGIS function to create spider diagrams? If I do not know the relationship between a point in layer A (stores) ...