Spatial Analyst is a extension within ArcGIS that provides a range of spatial modeling and analysis tools.

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7
votes
7answers
4k views

Extract raster values at points

How can I extract values from a raster by points. I prefer not in Arcgis. I prefer in Qgis or Mapwindow or other open source gis.
19
votes
6answers
7k views

Ways to Speed Up Python Scripts Running As ArcGIS Tools

This is a pretty general question. I just wondering what tips and tricks GIS programmers have used to speed up arcpy scripts that you import into the toolbox and run. I work most everyday writing ...
13
votes
6answers
7k views

Methodology for creating accurate drainage networks (and catchments) from high resolution LiDAR DEM?

This is not the first time I've stumbled over this issue; it seems that I am unable to generate a correct drainage network model and the resulting catchments from full resolution (1m cells) LiDAR ...
6
votes
1answer
702 views

Working around slow processing times in ArcGIS Spatial Analyst functions?

I am batch processing a large amount of distance functions (~50,000) using ArcGIS 9.3. In this version, using spatial analyst functions, it seems to be the case that users cannot parallelize processes ...
7
votes
2answers
2k views

How to calculate stream order for vector data without a DEM?

I have a shapefile which contains the streams that were digitized from a satellite Image. I would like to calculate the stream order for this data. The data does not exactly match the DEM that I have, ...
9
votes
3answers
727 views

Creating raster by randomly choosing cell value from multiple overlapping rasters?

I'm using ArcGIS Desktop 10 with its Spatial Analyst extension. How do I combine multiple rasters into one, always choosing randomly from the values of overlapping cells? I have an image that may ...
2
votes
0answers
602 views

Spatial Analyst Cell Statistics seems to give the wrong answer in ArcGIS 10.0

I have a script that calculates standard deviation for a list of grids using the Cell Statistics function in Spatial Analyst for ArcGIS 10.0 The syntax is this: stdevGrid = ...
4
votes
1answer
5k views

Thiessen Polygon delineation within a Feature

I am trying to create Thiessen (Voronoi) polygons, based on points within a defined shapefile extent. The output should be inclusive to the feature. The output I receive now is the rectangular area ...
2
votes
3answers
8k views

How to calculate Raster Area per Polygon?

In ArcMap, I have a raster file that contains 6 classes of landcover and a shapefile that is the census data (OA boundaries and their population). I want the area of each class in each OA? For ...
4
votes
2answers
675 views

Comparing two TINs created using ArcGIS for Desktop?

I have the following two files: LiDAR las file1 Let's give it a name LiDAR las file2, contains the same file1 data, where number of points randomly removed. So if file1 contains X number of ...
7
votes
2answers
2k views

Can shaded relief be “blended” with DEM colour ramp in ArcGIS to produce a more visually dramatic result?

Not being able to use true transparencies with ArcGIS colour ramps where only solid colours are allowed has me always wondering about how to improve the look of the surface in my maps without ...
9
votes
4answers
859 views

What Algorithm is used by ArcGIS Watershed tool?

Does anyone know what type of algorithm is used in the ArcGIS Watershed tool (in the Spatial Analyst package)? Very little information given on Esri's website ... but I suspect it may be some kind of ...
4
votes
1answer
455 views

Statistical analyses for survey against raster?

I am somewhat of a newbie to geostatistical analyses, but pretty familiar with GIS and remote sensing packages. I was wondering if anyone had suggestions on appropriate geostatistical analyses for a ...
8
votes
1answer
10k views

creating a dem from contours

I have a large set of contours that I received broken down into several different subsets. I have merged most of the subsets together creating a larger set of contours in three different files. I have ...
6
votes
3answers
5k views

Finding nearest raster cell value based on vector point?

I have two layers in ArcGIS: One is a vector point and the other is a raster layer. I want to append the value of the raster data grid to the vector point. The problem is the vector point is away from ...
6
votes
3answers
5k views

Clipping a raster using a polyline or polygon

I have a large raster created from values that cover the whole United States and Alaska which are both polygon and polyline features, this raster was caluclated using Spatial Analyst IDW ...
3
votes
1answer
507 views

How does cost allocation work?

Why, when I use the cost allocation function of Spatial Analyst, is space not allocated in all input source locations (as shown in image below)? In particular, the input raster has 18 spots while the ...
5
votes
1answer
490 views

Creating field with specified slope projecting from 3D polygon?

I am trying to figure out how to create a elevation raster from a known location (3D polygon) that projects at a specified slope (1%) for a specified distance(1-2 km). Does anyone have any idea how ...
3
votes
1answer
211 views

Grid-like lines appearing after using Curvature tool

I have been attempting to use the Spatial Analyst Curvature tool with mixed results. I originally tried to use it with a raster that was projected using a 1983 Teale Albers projection and the results ...
0
votes
1answer
111 views

How to measure Fracture in area using ArcGIS Cut and Fill?

I want to measure fracture in an area.I know I have to use cut and fill tool. But I wonder how to give input for this tool? it has Input before raster surface and Input after raster surface ! what ...
6
votes
1answer
3k views

RMSE between two rasters step-by-step

Can anyone show how to calculate the RMSE (root mean square error) between following two rasters step-by-step and discuss on the obtained results' min and max values, and how to interpret it. Thanks a ...
6
votes
1answer
3k views

ArcMap 10 - Extract raster cells from imagery based on RGB value

I've got some aerial photography (format: IMAGINE Image) which is detailed enough to see to fire hydrants and a shapefile of fire hydrants which was digitized based on some CAD data. My project is to ...
15
votes
4answers
2k views

Where can I find examples of fuzzy logic applications in ArcGIS?

The last ArcGIS version (10) includes two arctoolbox tools for fuzzy logic (Fuzzy Membership, and Fuzzy Overlay). Does anyone know where can I find some examples showing how they can be applied? ...
7
votes
5answers
2k views

What type of interpolation to visualize metal detection survey data?

I have about 500,000 points collected in a linear grid pattern over a 1 km2 area. The points were collected as part of a metal detection survey. Each point has X,Y and Coil Response mV (min -675.38 ...
6
votes
2answers
7k views

Dealing with NoData in ArcGIS Spatial Analyst?

When using Spatial Analyst I regularly have issues with NoData values cropping up in the data. Various tools appear to introduce NoData values regularly. These values then cause issues with ...
5
votes
1answer
206 views

Sum raster data visible from given point, by proportion of view

I am wondering if there is a tool that does the following (preferably in Arc but other options considered). Simple example: what proportion of the view from a given point on the landscape is occupied ...
5
votes
1answer
1k views

Does a Zonal Statistics value change when applied on a subset of data?

I have generated zonal statistics using feature zone data on a value raster. This shapefile contains about 20000 polygons and the analysis went without a hitch. While testing quality, I ran the same ...
3
votes
3answers
378 views

How to extract surface from air photo avoiding trees and buildings?

I am working with Drone air images. These are geotiff images and clearly portray trees and buildings. I need to first classify the image according to land cover distribution, then need to remove the ...
5
votes
1answer
341 views

Merging two DEMs in different pixel bits?

I have 2 different Digital Elevation Modeling (DEM). One is the state DEM and has 30m and has 16 pixel bit. I have a couple of smaller DEM that has 30m but they have 32 pixel bit. I know how to merge ...
3
votes
1answer
75 views

How can I create a constant slope DEM?

I wanted to create a DEM of constant slope say 1/3000. How can I proceed in ArcGIS 9.3? The area may be 1000m x 1000m or any other as per convenience.
3
votes
2answers
192 views

How to calculate the distance of sites to riverways

How do you calculate the distance of about 10 sites scattered across a region to bodies of water (rivers and lakes) using ArcGIS 10.1? I have the lat/lon coordinates of the 10 sites as a point ...
3
votes
1answer
1k views

Conditional reclassification of a raster

I am attempting to do a conditional reclassification of an NLCD land-use raster. I specifically want to reclassify all developed areas (classifications 22,23,24) that are near a road (classification ...
2
votes
1answer
132 views

Obtaining average value around polygon in raster for different cross sections?

I have elevation data in a raster, river (blue line) and the flooded area (black polygon) as shown in the image below: I want to find the water depth in the flooded area (inside the black polygon). ...
1
vote
2answers
131 views

Open source, Python option for Arcpy's Con tool?

I'm wondering if there is a method to perform a function similar to Arc's Con tool, using open source options in python. I have two rasters, one that shows locations of clouds and the other is just a ...
1
vote
1answer
383 views

GWR Result Issues

I am working with GWR to identify if there are any relationships between 'extreme' events and disease incidence. The use of GWR has been employed because I am working in a region where local ...
8
votes
3answers
1k views

How to combine corner-touching polygons into a single feature

I have created a polygon layer from rasters, and only have a single classification ID (and calculated acres) for each polygon. I would like to "dissolve" all touching features into larger, individual ...
7
votes
3answers
1k views

How to cluster points based on a kernel density?

I have a large dataset with 36k points representing commercial land uses, each with a field containing the square footage. I have run a kernel density analysis on this dataset, producing a raster ...
4
votes
1answer
765 views

How do I fill gaps in a raster to zero value cells?

I am trying to add some forest elevations to a DEM using ArcView. I have converted a polygon feature class of a forest into a raster with the same resolution as my DEM. Then I reclassed the forest ...
4
votes
2answers
198 views

Troubleshooting why ArcGIS Model works on one PC but not another?

Do you have specific expertise you could share of examples where an ArcGIS Modelbuilder has worked on one PC but not on another? Are there any issues between different Windows versions? There is a ...
4
votes
1answer
393 views

Which flow routing algorithms does ArcGis support?

Other than standard D8 are there support for multiple flow algorithms like FD8, DEMON, Dinfinity etc?
4
votes
2answers
2k views

How can I compare two point shapefiles that contain lat/longs and compute distance?

Greetings everyone, I have 2 sets of point shapefiles in ArcGIS (group A and B), each set has around 1000 entries that contain lat/long. What I want to do is compare Group A against Group B and figure ...
4
votes
1answer
1k views

Processing time using ArcGIS Hydrology toolbox tools in standalone Python script vs. ArcCatalog

My question is: what might cause the ArcGIS 9.3 Hydrology Toolbox Snap Pour Point and Watershed tools to run significantly slower in a Python script versus manually running the tools in ArcCatalog ...
3
votes
1answer
216 views

How to use Vector Ruggedness Measure (VRM) tool from ArcScripts at latest version of ArcGIS for Desktop?

I need to use the Vector ruggedness measure (VRM) tool available from http://arcscripts.esri.com/details.asp?dbid=15423. However, I am using ArcGIS 10.2 for Desktop and these tools are made for 9.0, ...
3
votes
1answer
304 views

How to exclude stations from IDW interpolation?

I have the following problem: I need to calculate an average precipitation amount on a catchment using an IDW interpolation. The interpolation is performed in a loop since each precipitation station ...
3
votes
2answers
668 views

Majority filter (minimum mapping unit) in ArcGIS with larger window size

I want to run the majority filter in ArcGIS with a window size of 4 or 5 i.e. greater than the default 3. Is it possible? Or some other command (or tool) which might help me achieve that? thanks!
3
votes
1answer
314 views

An error in raster calculator in Arcgis

I wrote and ran this formula in raster calculator in ARCGIS. But the following error gets me into trouble. Does anyone have a suggestion to overcome this? Here is the formula I wrote and the error ...
2
votes
3answers
109 views

Zonal Statistics as Table Tool

I have a slope dataset. I have a polygon shapefile with territory within the extent of the slope map. I have to calculate the real surface area of this shapefile using the zonal statistics as table ...
2
votes
1answer
403 views

calculating zonal statistics of raster data in multiple overlapping zones and combining them into one table

The aim here is to calculate the max, min, mean, range, sum, count and std of raster data contained in areas delimited by polygons (much like what the Zonal Statistics as a Table tool from Spatial ...
2
votes
0answers
517 views

How to assign values to a polygon layer based on nearest point in a point layer? [closed]

I have a point file depicting groundstations for rainfall measurment. I also have a polygon file representing districts of a state. I want to assign rainfall values in a particular district based on ...
2
votes
1answer
418 views

How can you make RasterToASCII_conversion observe environment setting output cell size?

I have two rasters (an ESRI grid and an IMAGINE image) that differ in projection, extent and cell size. I want to convert the IMAGINE to an ASCII, and want it to have the extent, cell size and ...