11
votes
4answers
2k views

Comparing two Digital Elevation Models (DEMs) from LAS files?

I have two Lidar las files, one is original let's say with X points. And the other is copy of the first las file but with Y points, where Y is less than X. Now, I want to compare how the Digital ...
8
votes
1answer
963 views

How to draw perpendicular lines in QGIS?

I have a situation like this: What I need to do is to connect each point to every line that is at most, let's say 200 m, away from the point. In other words, I need to draw a perpendicular line ...
6
votes
1answer
983 views

Creating a table containing all filenames (and possibly metadata) in a File Geodatabase

I need to create a metadata-table for all files in a File Geodatabase or Spatial Database. It would be awesome if it were possible to automatically be updated with new filenames, and possibly even ...
24
votes
3answers
19k views

What is the difference between WGS84 and EPSG4326?

What is the difference between WGS 84 and EPSG 4326? It seems like for a given dataset it might be both WGS 84 and EPSG 4326.
14
votes
2answers
4k views

How can I switch baselayers as a user zooms in to the map in OpenLayers

I have a map which overlays Open Street Map data on imagery for Pennsylvania. As a baselayer to the roads (and eventually other layers) I have two baselayers - Blue Marble NG and USGS EROS 1ft ...
13
votes
4answers
670 views

Migrating to Linux from Windows

I am looking at switching over a computer from Windows to Ubuntu. I have been a Windows user all my life and been using GIS for over a decade. I am curious about the migration to Ubuntu. Mostly, ...
12
votes
2answers
5k views

Specifications for GIS desktop hardware

I'm in the market for a new pc/laptop. Judging from what I've seen around here, a lot of people are discussing having a laptop for their personal GIS use. Portability is not an issue for me, so I'm ...
10
votes
4answers
654 views

Suggestions for simple mapping platform for alumni web site

I'm working on a proof of concept alumni site with a WordPress backend. I want to have a very simple map that shows where alumni are living. I'm thinking something like the Bing API or a simple open ...
9
votes
2answers
3k views

How to check Topology in QGIS?

I have two Shapefiles with Polygons ( City and Forerst) Is there a Plugin who is able check the topology (QGIS)? Like "Knots do not overlap" or something like that? I dont want that they overlap. ...
8
votes
2answers
1k views

How to count and rasterize polygon overlaps in ArcGIS?

How do you take a vector layer with overlapping polygons and turn it into a raster where each cell counts the number of polygons containing that cell? We are looking at polygons of fire burn areas ...
18
votes
3answers
1k views

How to calculate the intersection of 2 Circles?

I'm trying to figure out how to mathematically derive the common points of two intersecting circles on earth's surface given a center Lat/Lon and a radius for each point. Ex. Given: Lat/Lon ...
15
votes
4answers
7k views

Join non-spatial CSV to spatial data in QGIS

I have a csv which has postcode data in a field, but it is non-spatial e.g. no Easting and Northing. I have a shapefile with postcode in a field and some additional data. I want to join the csv with ...
8
votes
1answer
2k views

How to reproject a raster file in QGIS with datum transformation?

I want to reproject a tiff raster file from projection A (ETRS89/UTM Zone 32) to projection B (DHDN/Gauss-Kruger zone 2). The two projections have a different datum so I have to use a datum ...
7
votes
3answers
2k views

Using polygons to apply unique value to all raster cells within those polygons?

In ArcGIS 9.3, I have a raster file that I would like to "mask" with polygons, giving a single value to all the raster cells that overlap the polygons. How can I do this? Here's a screen shot, ...
6
votes
5answers
2k views

How to create points in a specified distance along the line in QGIS?

I want to use QGIS creating points along the line, but in specified distance. I found two GRASS tools in SEXTANTE Toolbox: v.to.points v.segment I tried v.to.points, setting the maximum distance ...
6
votes
3answers
8k views

Define Workspace for SDE Connection in Python

How do we define SDE Connection for workspace in Python Scripting. Its urgent please need your suggestion. Thanks
15
votes
3answers
3k views

How to call gdal_translate from Python code?

Is it possible to use some gdal API to call gdal_translate from Python code? I do not mean simply executing the gdal_translate.py from the file system, but rather call it somehow in code so I do not ...
14
votes
1answer
1k views

Voronoi polygons that run out to infinity

I have been working on implementing the voronoi.py script (Bill Simon's translation of Steve Fortune's code). According to the QGIS link it is basically the same code that I am working with, but the ...
12
votes
5answers
6k views

Obtaining extent of each polygon in shapefile?

In arcgis 10 and python I want to get the extent (xmax, ymax, xmin, ymin) info of each of the polygons in a shape file. I can get the extent of the whole shape file using ...
11
votes
2answers
2k views

Is it possible to export GeoPDF from QGIS?

Is their any plugin for QGIS which would help me in exporting the map document as a GeoPDF ?
10
votes
1answer
831 views

Is there a way to access QGIS plugins in Python?

Is there a way to access QGIS plugins in Python? I'd like to write a script to do some geoprocessing, and I'd like to use the clip, regular points and convex hull tools in fTools, as well as the Road ...
7
votes
1answer
2k views

Using PostgreSQL with QGIS and ArcGIS?

Is it possible to use PostgreSQL with QGIS and ArcGIS? i.e. one database for different clients. Is it anything that I have worry or any problems to use the DBMS from two different software? I know ...
7
votes
4answers
3k views

Site to download al USGS Topo Maps in bulk

I am trying to create seamless topomap WMS or TMS layer that covers the entire US (not interested in geo-pdfs). To do that, I need either the rasters (geo-tiffs, etc) or preferably vectors (whatever ...
6
votes
4answers
4k views

How to change the order of features in a shapefile?

I have a shapefile and I want to change the order of the features. Is that possible using ArcMap?
17
votes
3answers
571 views

How much Water on Earth(USGS) : A Wrong Map representation?

I happened to read a USGS article, How much water is there on, in, and above the Earth? showing a representation of all the water(which includes water from Oceans, Seas,Bays,Ice caps, Glaciers, ...
11
votes
6answers
940 views

How to implement value-by-alpha map in GIS?

I've been doing some background reading about cartograms recently and stumbled upon interesting alternative - value-by-alpha maps. Concept is described in more details here and full paper is ...
9
votes
2answers
1k views

Which function for creating a POINT in PostGIS?

When defining a Point in PostGIS, when do you decide to use which of the following? ST_SetSRID(ST_MakePoint(lon,lat),4326) ST_SetSRID(ST_Point(long,lat),4326) ST_SetSRID(ST_GeomFromText('POINT(lon ...
8
votes
1answer
1k views

How to compute the bounding box of multiple layers in lat/long?

I am writing an application to performance test all kinds of map services, primarily AGS 9.x, AGS 10, and WMS 1.x. Part of the application involves generating random bounding boxes for individual ...
7
votes
3answers
4k views

Tutorials for geoserver

Do you know any sources from where i can learn how to use geoserver? I know this two sites: http://geoserver.org/ - which in fact is not working (at list at the moment) ...
6
votes
3answers
3k views

Why don't my Shapefiles and OSM data overlap in Quantum GIS?

So I'm pretty new to GIS, and I'm working on a mapping project using data for Vancouver, Canada. I want to combine Open Street Map data along with data provided by the City of Vancouver. But the City ...
5
votes
1answer
860 views

Shortest distance from point to line (big dataset)

What is the best method to calculate the distance from the nearest road for a series of address points in QGIS, having a very big dataset? (QGIS 2.0.1, Win XP) I read the answers to previous similar ...
5
votes
2answers
4k views

Interpretation of ArcGIS Kernel Density legend parameters

In ArcMap 9.3 I've used Kernel Density to map various incidents, but the resulting shapefile doesn't display any units of measurement. Is there a good, not-to-technical source that would explain in ...
4
votes
1answer
1k views

OpenLayers Plugin Error: latitude or longitude exceeded limits

I'm aware the 'traceback' OpenLayers plugin error has been dealt with before, so apologies for raising the issue once again. Unfortunately for me, the solutions posted were way over my head, e.g. ...
4
votes
2answers
378 views

Does Calculate Value (Model Only Tool) work correctly in tools run in Batch?

Am I correct that if my model has a model-only tool (Calculate Value), and then I run the model as a batched process, it will not run the Calculate Value expression? I wrote a model to upload, ...
3
votes
1answer
3k views

Elseif Conditional Statement in QGIS Field Calculator

I am trying to write an ELSEIF conditional statement in QGIS Field Calculator (version 1.8.0). I have used an example I found online: CASE WHEN val < 0 THEN 'negative' WHEN val = 0 THEN ...
2
votes
1answer
520 views

Help with Python script for exporting mxds into pdfs!

I have written a python script to export my mxd into a pdf (not using data driven pages). I am getting the error that my mxd path is incorrect! I have included my script below. Any help would be ...
10
votes
4answers
862 views

How to calculate the visible sky percentage

Hi I am writing a project and I am stuck: can anyone explain as simply as possible how to calculate the visible sky percentage? I have done a satellite survey and have worked out the height of ...
8
votes
7answers
8k views

Corrupt shapefile. How to fix

I have a shapefile I was working on (ArcGIS 9.3) get corrupted somehow and it gives me the error "Number of shapes does not match the number of table records.". What I would want is to recover this ...
7
votes
1answer
875 views

Inserting newlines in Rectangle Text elements via ArcPy causes overlap?

I ran across an issue the other day when I tried to use ArcPython's mapping module to edit rectangle text elements with newlines (\n) in an ArcMap document. Here's what the output looked like: ...
7
votes
2answers
574 views

Reordering polygon shapefile permanently?

I've written a script which produces a polygon shapefile of the extents of all the thousands of rasters in our library. I want to organise the FID so that the files with the largest extents are on the ...
6
votes
3answers
2k views

Is it possible to postprocess Trimble .ssf files without Trimble Pathfinder Office?

Is it possible to postprocess Trimble .ssf files without Trimble Pathfinder Office (differential correction - our sporadic use does not defend realtime correction subscription) ? We only need the ...
6
votes
1answer
1k views

Difference between Geographic-3D and Geocentric CRS

I'll start with the OGP definitions: Geographic. A coordinate reference system based on a geodetic datum and using an ellipsoidal (including spherical) model of the Earth. This provides an accurate ...
5
votes
1answer
566 views
5
votes
3answers
2k views

I exported a DXF from QGIS, but it won't open in AutoCAD

I'm new in QGIS and here is my problem: I exported a DXf from QGIS by right-clicking on the layer. Then tried to open in AutoCAD 2000. That did not work. AutoCAD gave a failure-message: Unknown ...
5
votes
2answers
5k views

How to calculate polygon areas and perimeters?

If I load a polygon layer and make a new column, how do I fill that column with the 1) area of each polygon and another column with 2) the length of the perimeter of each polygon?
3
votes
2answers
830 views

Is it possible to colour areas between (vector) contours?

...without making it a DEM first? Joshdoe seems to have done so ("Styled in QGis") here but doesn't say how. Thanks!
3
votes
2answers
6k views

Create polygon layer from polyline layer

Our systems expect polygon shapefiles, representing a collection of non-intersecting and geometrically valid (multi)polygons. Specifically, farm fields. We often receive our representations of farms ...
2
votes
1answer
96 views

How to set up a 3D plane in ArcGIS?

I need to model a fault plane below the earth's surface and find distances from different points on the surface of the earth. I know the dimensions of the plane and its orientation but I can do that ...
1
vote
2answers
816 views

Why should we use a proxy script for Apache, Geoserver, OpenLayers?

I can't understand why we use proxy( OpenLayers.ProxyHost)for WMSGetFeatureInfo request in open layer. I am using open layer 2.10 ,apache-tomcat-6.0.35 and geoserver. Why we use proxy? How should ...
20
votes
4answers
4k views

How to bypass 10 character limit of field name in ShapeFiles?

I'm exporting geometry with attached text attributes from oracle database to esri shapefile format (.shp) with Java and Geotools library. Attribute columns in our database have names with more than ...

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