Geographic Information Systems Weekly Newsletter
Geographic Information Systems Weekly Newsletter

Top new questions this week:

What is the difference between Coverage, Shapefiles and Geodatabases in ArcGIS?

I was wondering about the difference in spatial data storage methodology used by Coverages, Shapefiles and Geodatabases in ArcGIS. Coverage was the initial format, followed by Shape Files and now …

arcgis-desktop shapefile esri-geodatabase coverages  
asked by Abhishek Potnis 9 votes
answered by Alex Tereshenkov 10 votes

Reducing elevation from DEM using ArcGIS for Desktop?

I am so curious how would I strip off elevation from the DEM. I don't know how I would explain it further but I have attached an image to clarify this. I wanted to eliminate the area shaded with …

arcgis-desktop arcgis-10.1 arcmap dem elevation  
asked by vklopt 6 votes
answered by Michael Miles-Stimson 5 votes

What is the difference between Create Thiessen Polygons tool (ArcGIS) and Voronoi Polygons tool (QGIS)?

Is Thiessen polygons the same thing as Voronoi polygons? I am using ArcMap 10 and also QGIS 2.4 and I would like please to know the exact difference (If any) between the two methods.

qgis arcgis-desktop voronoi-thiessen  
asked by marika 6 votes
answered by WhiteboxDev 10 votes

Implementing INSPIRE Metadata with Geodatabase

I would like to begin by saying that I have never implemented INSPIRE metadata with my spatial datasets before. I am undertaking a project which requires my geodatabase metadata to be in the standards …

arcgis-desktop esri-geodatabase metadata encoding inspire  
asked by RicJ 5 votes
answered by Mapperz 6 votes

Adding Route Shapefile (PolylineM) to QGIS?

I'm new to QGIS (and to this amazing forum as well) and I already have an issue : I received a Route Layer in SHP format (PolylineM). I've easily loaded this file into QGIS but it doesn't seem to …

qgis shapefile linear-referencing route  
asked by hugues 5 votes
answered by underdark 1 vote

Calculate the common area between polygons using python?

I am trying to calculate the common "empty" area between the neighbouring polygons in order to calculate the porosity volume (the red area in the image) My idea was, first to use Convert …

arcgis-desktop arcgis-10.1 arcpy  
asked by Yahya Ghassoun 5 votes
answered by WhiteboxDev 3 votes

Drawing parallel lines inside polygons (Well Paths)

I would like to take a polygon feature class with multiple irregular polygons, and have Arc draw parallel lines inside of each polygon. Ideally, it would be nice for Arc to figure out the angle of the …

asked by Tx_Dan 4 votes
answered by cndnflyr 3 votes

Greatest hits from previous weeks:

What free programs should every GIS user have installed?

Note: This question is specifically about installed, desktop software. There is another question specifically about free cloud-based software and services. I'm not necessarily referring to ESRI …

open-source development software-advice free-software  
asked by Nick Ochoski 131 votes
answered by blah238 97 votes

How to measure the accuracy of latitude and longitude?

I am very new to GPS stuff. Suppose I have latitude and longitude as 19.0649070739746 and 73.1308670043945 respectively. In this case both coordinates are 13 decimal places long, but sometimes I also …

lat-lon accuracy precision  
asked by Saurabh 82 votes
answered by whuber 162 votes

Can you answer these?

Overwrite a table in CartoDB

I need to overwrite a table in CartoDB using the Import API, but the system instead of overwriting the table, it creates another one with the same name and attaches an id auto-generated. For …

asked by laura 2 votes

Using ArcGIS Online for public participation?

We have an ArcGIS Online Organizational account setup with several maps facing the public. I would like to create an application using one of our maps that has the added functionality of allowing …

asked by Mercator 2 votes

Model Builder Query by date

I've created a model that does several spatial joins based off of a lat/long in a table. In the table, I have a "Modified_date" which gives year, month, date, time. This model is set to run …

arcgis-desktop modelbuilder sql query-layer definition-query  
asked by Zack 2 votes
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