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5

Distance calculations that assume shortest distance on the Earth will always be faster than geometry because geometry can be in any projection, and there's no way generally to know that the shortest path in that projection is the 'shortest path' and so you need to go to ellipsoid calcs and potentially insert more vertices for the curvature from the source to ...


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WGS 84 and ETRS 89 are two geographic coordinate systems (Lat/long). With those coordinate system, you will measure distances on the surface of the ellipsoid. WGS84 and ETRS 89 use almost identical spheroid (see below), so in most cases you will not see any difference between the 2. You are projecting your data in Universal Transverse Mercator zone 35 ...


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If you have the data in Excel you'd probably do better doing the calculation in Excel! The Haversine formula (find it here: http://www.movable-type.co.uk/scripts/latlong.html) will give you the distance between two pairs of latitude and longitude.


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One way would be to use ICurve QueryPointAndDistance to and get the DistanceAlongCurve value for your 'B' point. Then call ICurve.GetSubcurve twice (with the DistanceAlongCurve + 2 and DistanceAlongCurve - 2) and the fromDistance parameter as 0. And the asRatio as false. The "To" points of the resulting subcurves would be your 'A' and 'C'. ...


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Best explained from Microsoft in Spatial Data Types Overview: Measurements in spatial data types In the planar, or flat-earth, system, measurements of distances and areas are given in the same unit of measurement as coordinates. Using the geometry data type, the distance between (2, 2) and (5, 6) is 5 units, regardless of the units used. In the ...


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There is a tool in the analysis toolbox called symmetrical difference that you could use. You would put all your buffers in one layer and your counties in another layer. Then the tool would tell you all the areas in the counties that don't intersect any of the buffers.


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If I understand you right, you want the opposite of a buffer. Then first, you need a polygon of your area of interest (AOI), say the border of a state or something like that. Second you calculate your distance buffers which you could clip from the previous AOI polygon. That should give the "outside" of the buffers.


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My suggestion is based on a method I apply to group smaller subcatchments into larger. There are no streams, thus 1st step to compute Euclidean minimum spanning tree: I guess it is some sort of optimisation already. Pick your sink and create directed graph. Picture below shows "Flow Accumulation" in links, i.e. count of nodes discharging into it: ...


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I believe the Euclidean Distance (Spatial Analyst) tool will accomplish what you're after. The tool creates a raster file where each cell displays the distance to the nearest input feature. For your weighted analysis, you could then reclassify the EucDist raster into discrete distances (eg 500-1000m). ...


1

If I understand correct, your question consists of 2 parts: 1. How to get many linestring to merge to 1 2. How to get the point 1000 km further down the road from point 1 Part 1 needs some more explanation from you. It seems you already did a linemerge and that works for me as well with the data you give. Maybe you can post a new stackexchange question ...


1

I found the answer to the original question, and will therefore answer it here, and make a new question. Turns out that the points that are omitted are the ones that match exactly , or that has 0 metres between them. New question will be about how I can make a distance matrix with both the nearest points with distance >1 m and the ones that match ...


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The error is no doubt because the earth radius in your formula is not exactly the same as that used by ArcGIS. In fact, seeing as the earth is not a perfect sphere, the radius is different at the equator as it is at the poles. Probably ArcGIS corrects for that. However: in the Haversine Python script, it has: Base = 6371 * c If you calculate the ...


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I'll speculate that what the GeoDjango docs are trying to say is that if you have geographic (lat/lon) data, and you want to perform range queries on that data (like ST_DWithin) in meters rather than units of degrees, then you are better served by using the geography type, which uses meters natively. The geography distance calculations themselves (ie ...


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Using the convex-hull of a polygon this is quite easy. First you have to include your two points in the set of points building the polygon. Now build the convex-hull for that point-cloud which is always the shortest path around the polygon. There is a GP-tool at Data Management called Minimum Bounding Geometry which you may use for this.


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I'm in a similar boat as you and this site has been more than helpful: http://www.ing.unitn.it/~grass/docs/tutorial_64_en/htdocs/esercitazione/network_analysis/index.html It goes through the various v.net tools in GRASS - I'm not a coder or anything, but I've become pretty familiar with GRASS over the past few months with the help of this site.



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