Lots of people have been asking me about terrain derivatives lately, and I've been putting off blogging about them for a while because I just didn't know where to start. Instead of one master post with all the things I decided to split it into some more manageable chunks-- for both your sake and mine.… Continue reading What are terrain derivatives?
Tag: GIS
EPSG Numbers and Coordinate Reference Systems
Over the last month or so I've had a little series about how we describe positions on the globe and how we visualize spherical space on a 2D map. I started with big picture information, like why we care about map projections. Last week began giving more concrete advice for picking a projected or unprojected… Continue reading EPSG Numbers and Coordinate Reference Systems
Selecting a Projection for Spatial Analysis
More map making! When you're first starting a new project and have data files in different projections, you can still view all your data together at once, using something called on-the-fly projection (a common feature of most GIS software). On-the-fly projection displays all your files using your "project CRS" and lets you have map layers… Continue reading Selecting a Projection for Spatial Analysis
What is a Shapefile?
Shapefiles are one of the main types of data you work with in a GIS. I have a description of GIS here, and an intro to the other basic data type (rasters) here. Shapefiles are vector data, and vector data comes in three basic forms: polygons, lines, or points. Polygons are shapes that take up… Continue reading What is a Shapefile?
Data Sources for Satellite Images
Satellite images have a wide variety of uses. They make a great backdrop for other maps and can give you an idea of land use in your area. The greenness in summer images can give you an idea of relative productivity. Bare ground photos taken when the ground is near field capacity can give you… Continue reading Data Sources for Satellite Images
Raster Data
If you work with spatial data, you'll likely come across rasters at some point. Raster data can be thought of as a grid of cells, and each cell contains a value. This value can be continuous, such as in an elevation model where the value in each cell represents feet above sea level. The Crop… Continue reading Raster Data
GIS Workshop in Columbus, OH
Byrd Polar Research Center and University Libraries are offering another basic GIS course. I heard great things about last year's workshop and wanted to share this opportunity with you. This year's focuses on Google and Esri based tools. Students are encouraged to bring laptops and mobile devices to get some hands-on experience. If you're in… Continue reading GIS Workshop in Columbus, OH
What is GIS?
People ask me what I'm up to, and frequently my answer is "oh, just working on some data cleaning in GIS." This usually leads to the follow up question, "What is GIS?" Turns out that's kinda hard to answer. GIS stands for Geographic Information System. Note the word geographic-- the information involved has coordinates or… Continue reading What is GIS?
Spatially Challenged 