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Common Raster Data Sets

There are a huge number of different types of raster data available. Some of these can be categorized as:

Topos

Topographic maps including 24k, 50k, and 100k, have been around for a long time and are still one of the best reference data sets. These images are not very attractive because they were actually "scanned" from paper copies of the maps. They are also going out of date and newer "Digital Line Graphic" versions are becoming available.

A topographic image

Topo maps can be downloaded from the USGS web site.

DEMs

Digital Elevation Models (DEMs) are one of the most commonly used rasters for GIS folks and we'll be making other rasters from DEMs in just a bit.

A DEM rasters

DOQQs

Digital Ortho Quarter Quads where black and white aerial photos that were taken periodically by the US government. These images have largely been replaced by sources such as NAIP but they still come in handy in remote areas. Below is an image of the capitol mall in Washington DC.

DOQQ

LandSat

LandSat is one of the most valuable and commonly used data sets we have. It extends over 30 years and scans the entire earth twice a month.

Image of the LandSat satellite

The LandSat satellite orbits the earth in a tilted polar orbit giving it the characteristic tilted images you may have seen before. Below is a sample LandSat scene that is shown the agricultural land highlighted by moving the infrared band to the red band.

A sample image from LandSat

NLCD

The National Land Cover Dataset (NLCD) classifies each 30 meter pixel in LandSat scenes to give us a code for each pixel. Below is a sample NLCD image for Washington DC. You can see that this is a high commercial and high intensity residential area with some open water.

Image of NLCD for Wasginton DC

This dataset makes it very easy to perform operations such as change detection. Below are NLCD images for the same area over a 14 year period. You can see the increased human development over this period and the narrowing of the water ways.

1992 2001 2006
LCD from 1192 NLC from 2006 NLCD 2006

 

MODIS

The Moderate Resolution Imaging Spectro-Radiometer sensor scans the entire earth at 250meters per pixel but twice a day.

modis satellite

Below is a MODIS image of Utah and Colorado during serval large fires. The fires have been colorized red and because this data is available twice a day, MODIS quickly became part of fire fighting world-wide.

An image from MODIS of fires over Colorado

Below is a land cover map for MODIS at a global scale. MODIS and other satellites provide us with new data to create valuable derived layers to see portions of the earth or the entire earth in a way that could not be imaged by our grand parents.

Image of MODIS landCover data for the world

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