Tagged Questions

The process of extracting geographic, statistical, geometric, or scientific information from one or more related collections of GIS features and data.

learn more… | top users | synonyms (2)

1
vote
0answers
17 views

Get pixel values ascii 50 files

I´m working with photos from a cam. The cam is arranged to take ndvi values instead of RGB for each pixel. I have several folders with 50 pictures in each folder as '*.asc' files the pictures. I am ...
2
votes
1answer
33 views

Clip_Management seems to delete shapefile?

We have some python code that clips a very large shapefile for further processing. We can see the process create all the output files, but then just as the process is finishing, they get deleted. ...
4
votes
3answers
77 views

General steps to create watershed boundary

I am a very beginner of ArcGIS. I got this CD of GIS files of a city and intend to work on watershed management. There are different file names in different formats on CD. Like .shp, .shx, .dbf, ...
2
votes
1answer
36 views

Performing equivalent of ArcGIS Identity_analysis (line with poly) using PostGIS?

I've got a section of arcpy code that I need to port PostGIS: Identity_analysis with the in_features being a line featureclass and the identity_features being a polygon featureclass. I'm primarily ...
1
vote
0answers
17 views

How to produce a simple ZTV/ZVI in openWind?

I'm struggling to get to grips with openWind. I need to produce a ZTV showing a 5km radius around the chimney of a proposed industrial development. I'm not sure of the height of the stack yet but for ...
9
votes
5answers
287 views

GIS analysis to find duplicate geometries

I have a big shapefile that contains all the buildings and houses of the town that I work in (approx. 90,000 features). The data of the buildings/houses are saved by the town's surveying engineers and ...
0
votes
1answer
34 views

Looping Summary Statistics on changing field name

I am trying to calculate summary statistics for a number of shapefiles, which is easy enough, but the field name for each shapefile is different. The field name is identical to the file name if that ...
4
votes
1answer
50 views

Is it possible, and if so how, to effectively classify vegetation types using false near infra red imagery?

Background : I use near infra-red imagery to delineate wetlands and water bodies with good success. It's also obvious to distinguish between new healthy vegetation and older growth and land areas with ...
1
vote
0answers
52 views

How to batch process near feature distance in ArcGIS

I have 2000+ point shape files. These are all GPS tracks. I want to calculate the distance from each point to the nearest feature (road, train line, restaurant etc) within a 30 meter radius. I am ...
5
votes
2answers
376 views

Are GIS Analyst salaries going to always be so low? [closed]

I regularly see GIS Analyst job postings (often in very expensive cities) asking for a plethora of experience paying in the $40k - 60k a year range, many are even below $40k or $30k. Considering the ...
0
votes
0answers
21 views

Raster Analysis Grid (Interpolation) Crashes [on hold]

Upon clicking on "Grid (Interpolation)" QGIS crashes. I running QGIS 2.2.0-Valmiera on a Mac with OS X 10.9.4 Thank you for any trouble shooting guidance
3
votes
1answer
57 views

Statistical Analysis of Shapefile Proximity within Raster Image - ArcMap10.1

I have a raster image that has been reclassified into 15 equally incremented values/levels. This raster represents "sinkhole risk" in a certain county. So level 1 is the lowest risk region and level ...
0
votes
2answers
47 views

Frequency analysis and overlay analysis

Am new to gis and I hope to find help here. I am working on a research that requires that I overlay conditions of drainage systems and quality of healthcare in a coastal state to get areas which have ...
4
votes
2answers
101 views

Identify cluster centroids

I have a data set of points which are grouped into clusters like so: I'd like to use ArcGIS or Python to create a point layer of the centroids of each cluster but I can't seem to find the right ...
0
votes
1answer
97 views

How to colour contour lines in .shp file when the lines are not meeting in QGIS?

I am doing bathymetry analysis, where I would like to color the contours one by one in the case land is rising (or sea level going down). There is a comprehensive explanation about coloring contours ...
2
votes
0answers
61 views

FME - Raster Algebra and Multicriteria Analysis

I'm trying to use FME to do some raster algebra for some Multi-Criteria Analysis. At the moment, I have three rasters, all with the same extents and resolution: Slope, Hydro, and Infrastructure Mask. ...
1
vote
1answer
69 views

How to dissolve adjacent parcels by same owner but include those parcels located across the street with the same owner?

In trying to determine the total contiguous stream length per landowner, I dissolved parcels by parcel owner name attribute and intersected these dissolved parcels with streams. However, dissolving ...
1
vote
0answers
66 views

network based interpolation methods, which one could I use?

I need to interpolate traffic data consisting in raw number of vehicles passing across certain points, where counters are. It is evident I haven't a uniform distribution of points and values about ...
0
votes
0answers
84 views

Finding shortest cumulative route (i.e. best 'hub') between networked points

How do I find the shortest cumulative route (i.e. best 'hub') between networked points? I have a dataset where some but not all of the points in the network connect to each other, however it is ...
3
votes
0answers
63 views

How to create cost surface for least cost water transport analysis?

I am working on a project to derive least cost pathways between sites by dug out canoe travel. Has anyone worked on a similar project or found a function like the Tobler hiking function that can be ...
1
vote
0answers
33 views

Analyse effect of groups on raster maps

I work with a mechanistic model that uses climate data to simulate some specific output for different time steps and spatial locations. Now I want to investigate the effect of different climate data ...
9
votes
1answer
220 views

When dealing with rasters of varying resolutions should one resample to the highest or lowest resolution?

I'm looking for recommendations on best practices for dealing with raster data layers with different resolutions and projections. The advice I've been given is to always resample to the layer with the ...
3
votes
2answers
40 views

What type of remote sensing methodology is commonly used to locate and track the movement of woodland caribou herds?

I am most curious whether it is possible to use Landsat or other freely available imagery (but info on any other method would great as well) to locate and track the movement of woodland caribou herds ...
1
vote
1answer
73 views

Calculating distance between borders when one polygon inside another polygon?

I am brand new to ArcGIS and having some trouble. I would like to calculate the distances between the border of one polygon to another polygon. However, these polygons overlap. Thus when I use the ...
0
votes
0answers
56 views

Efficient manner to buffer streams with multiple attributes?

I need to buffer a very large, complex hydro vector layer based on different water quality designations and surrounding slope. Different water quality classifications have different buffer ...
0
votes
0answers
43 views

Why don't my service area polygons follow my network?

I have found a few similar questions, but no good answers, so here goes another Service area question: I'm working on creating a walking distance layer from Parks, and have a road network set up with ...
0
votes
0answers
98 views

Calculate ANOVA using GIS

It's possible to calculate a statistic like ANOVA using GIS. I'm using ArcGis, but there's any GIS software to calculate it? Thanks,
1
vote
0answers
59 views

How to Create Polygon shapefile based on change in point value?

Is there a function in ArcGIS that would take analyze the adjacent point or polygon based on percent difference. If the adjacent value is within less than the percent it would dissolve otherwise ...
2
votes
1answer
124 views

Is there a limit to the amount of data in a spatial join in QGIS?

I am using Quantum GIS and trying to spatially join a point grid with polygons that are overlapping. If I get the sum of intersecting features, then I can get a good raster value. Well, every time I ...
1
vote
1answer
58 views

ArcGIS “Zoom to layer” scale

I'd like to quickly inspect the features in a feature class by double clicking the row in the table view and looking at the surrounding base layer. This works, but the feature fills the screen, so I ...
1
vote
1answer
74 views

How does the tolerance influence QgsGraphBuilder and tieing of points?

I am developing a script which uses OpenStreetMap data to calculate the distance (over the road network) between each building and the nearest hospital. To do this, I mainly follow the official ...
1
vote
2answers
272 views

Creating flat end type polylineline buffer in model without ArcGIS advanced

I have a polyline split into many short segments and would like to create a flat end buffer for each individual segment (not "dissolve" them all into one feature). Is there any way to do this in an ...
3
votes
2answers
269 views

Creating square buffer in qgis

How can I create a buffer with square ends along a line segment in qgis? I've buffered lines using v.buffer in the GRASS plugin, but the -c option for square ends is not exposed in that interface. ...
2
votes
0answers
68 views

Finding obstructions along a stream with LIDAR

I'm trying to find obstructions to boat traffic (downed trees, collapsed bridges, etc) along medium sized streams (5-15m across). The obstructions may or may not obstruct water flow. I have good ...
2
votes
1answer
168 views

GIS Analysis - best way to combine and display demographic data?

I am currently undertaking a demographic research project for my employer. We have the data on income, age, sex, language, transport etc and I have mapped most of it and created some thematics of said ...
3
votes
1answer
86 views

Analyzing spatial differences: conceptual and technical questions

My question is both conceptual and technical, but more conceptual than technical. It's a little long and multi-pronged, but I figured the best answers would consider everything, so thanks for bearing ...
3
votes
1answer
88 views

Add more info in the attribute table after executing “Line intersection” in QGIS

I have executed the "Line intersection" tool on a road shapefile. This is under Vector > Analysis Tools > Line intersections. I get an output with attribute table having just two columns: type_1 ...
18
votes
4answers
1k views

What are the benefits of hexagonal sampling polygons?

I am always on the lookout for useful methods to sample or partition study areas (usually in the form of raster datasets) into smaller units. Recently, I read an ESRI blog post about a new tool for ...
-2
votes
2answers
112 views

How to get layer extension info via Arcpy

I want to get file format of a layer with using Arcpy. I am writing a tool that needs to take raster or feature extension like SHP, TIFF etc. Which functions should i use ? Note: I use ArcGIS 10
0
votes
0answers
90 views

Selecting ideal locations using vector data - location analysis ArcGIS

Wondering if I could get some advice on how to approach a problem. I have 10,000+ polygons of varying size and shapes which I would like to use in a location based analysis. I have a set of parameters ...
4
votes
1answer
242 views

What is the FME Equivalent to the ArcGIS Union tool?

I'm attempting to union 2 large featureclasses in ArcCatalog, QGIS, and FME. What is the transformer that would be equivalent to the ArcGIS Union tool?
3
votes
0answers
84 views

Calculate field of view / angle of a point to a shapefile

I am trying to automate a calculation of the blocked fraction of a field of view from a point to a shapefile. I.e. find α in , such that α / 360 gives me the fraction of the field of view covered ...
2
votes
1answer
327 views

GTOPO30 Slope analysis in ArcGIS 10.1 [duplicate]

Using surface - slope analysis tool box. All values for the slope calculation are in between 80 and 89. There are no values below 80. What am I doing wrong?
2
votes
0answers
153 views

Our best table-analysis with GIS? [closed]

Sometimes I think about possible analysis using GIS models (I use QGIS 1.8), and I always think about few types of visualization techniques: demographics, traffic flows, distance ones... Thanks to ...
1
vote
1answer
81 views

How to select a part of a land cover type a certain amount of feet away from another land cover type

I have raster Landcover type Urban combined with Forest all within the county raster perimeter. I want to make a layer of only the forest cells that are more than 500 feet from an urban cell, so that ...
0
votes
0answers
142 views

Linking two Models together in ModelBuilder

I am trying to link two separate models that iterate thought two different feature classes together into one, however I am having a small issue. When I bring in the sub-model into the larger one it it ...
2
votes
1answer
86 views

Is it possible to automatically update a Buffer FeatureClass when creating new features?

Is there a way I can update the results of my Buffer analysis? I have a roads FeatureClass, and I've built a buffer for it. I will still make edits to the road FeatureClass. Let's say I add a new ...
5
votes
1answer
758 views

Split polylines at polygon boundaries in QGIS

I have a set of contour lines and a polygon set containing glaciers. Because I want the glaciers to have blue contours, I need to split the contour lines at the glacier boundaries. I can achieve this ...
3
votes
1answer
282 views

how to calculate the basin length - which point to which point and how in arcgis 9.3?

This is the area of my research.I have calculated area using area and perimeter using arcgis 9.3 for doing morphometric analysis of the area.but i dont know how to calculate the length of the basin ...
1
vote
2answers
2k views

Reading National Elevation Dataset (ArcGrid/GridFloat/IMG) with python only tools

I've found high precision elevation (1/3 - 1/9 arcsecond resolution) data from the National Elevation Dataset provided by the USGS. It comes int IMG, Arcgrid, and GridFloat formats. I know ArcGrid ...