Tag Archives: GIS

Accuracy, Precision, and Resolution in GIS and Everyday Life

It’s very helpful to know the difference between Accuracy, Precision, and Resolution, not only in GIS but in everyday life and especially in science and engineering. Below are some resources that will help you learn the difference.

This first source is a video by Dr. Colin D. MacLeod, founder of “GIS In Ecology” (http://www.gisinecology.com/) . The intro text is as follows:

When collecting data that will be used in a geographic information system (GIS), it is important that you record it properly. In order to do this, you need to understand the difference between accuracy, precision and resolution. This short video provides a brief and easy to understand introduction to these concepts using target-shooting as an analogy.

The video is on YouTube at http://youtu.be/5HkZ2iM0cTE and embedded below.


This next source is an excellent explanation of Accuracy, Precision, Resolution and Sensitivity by Measurement Computing Data Acquisition, a data acquisition vendor.



Below is an interesting quick read on a GIS professional’s view of the rapid advance of GIS data quality, including accuracy, precision, and resolution.



Finally, this last source contains an interesting discussion on error, accuracy, and precision, and its importance in GIS.


ArcSDE No Longer Needed in ArcGIS 10.1

Here’s a good link for Esri/ArcGIS for Server users and those who otherwise need to connect an ArcGIS-based application to a database. With ArcGIS version 10.1, much of the Spatial Database Engine (SDE) functionality has been included in the Engine, Desktop, and Server products. Esri has not yet said that it’s getting rid of SDE, but I consider it deprecated and recommend people move to using a direct connection as soon as practical.


This excellent link contains questions by Esri users and answers and explanations by Esri staff on whether/when you need to use SDE with ArcGIS 10.1.

OGC Drops Esri Rest Specification

This is interesting. The Open Source Geospatial Foundation (OGC) recently decided to withdraw the GeoServices REST Specification, known to many of us Esri users as the “ESRI REST API,” as a proposed standard. This looks like politics getting in the way of progress.


For those who don’t know, Esri can be thought of as the Microsoft of GIS, for good and bad. Esri is a good, generally ethical company, unlike Microsoft, but it dominates the geospatial world as Microsoft does for operating systems and office software suites. Like most big companies, Esri can get in the way of progress at times and is generally unwilling to share it’s proprietary code with the world. But it makes some excellent products, particularly if you need to do serious geospatial analysis, need to serve huge quantities of geospatial data to thousands or more users, or use GIS in your daily work.

I’m not sure what’s going in with the OGC here, but the act of dropping this Esri-created spec will result in OGC being out of the loop on a de facto standard for geospatial services and underrepresented in a major aspect of GIS technology.

The article’s worth reading if you are involved in the geospatial world.

A Look at Raster Compression, Pyramids, Time, and Space

For those interested in geospatial technology: This is an excellent article on data formats, the relative sizes of a given amount of data stored in each, overviews for each format, and the relative time required to read/serve the data in each format. The knowledge presented here should be helpful in determining what data formats you deploy with your system.