Custom Maps Using GIS
By: Vaiden Bloch, Northwest Management, Inc.
Prior to the arrival of computers and digital data, foresters relied on paper maps and aerial photography to assist in managing their lands. For a long time, USGS topographic maps and USGS Ortho Photo maps, as well a 9”x 9” stereo pair aerial photography were the medium of choice for mapping. Base maps were developed from these products for the area of interest and map layers were drawn on clear Mylar overlays identifying important features such as timber stands, streams, roads, and soils. Aerial photography was used to update maps, but aerial photography for small landowners was often dated, hard to acquire and expensive. With out aerial photography to update maps, foresters would use conventional surveying techniques to calculate acreage and determine the location of features such as roads, property lines and harvest unit boundaries. Then along came computers, GIS, digital data and the internet.
GIS (Geographical Information System) is a tool that uses computer technology, digital data and analytical processes to manage and display geographically referenced information, and make maps. GIS enables map layer overlay, modeling and querying to answers questions and provide information not possible with paper maps. Digital map data is widely available on the internet. Since GIS is an integral part of all government agencies and universities; map layers are continually being created, updated and improved. In areas where specific mapping information is not available, GPS (Global Positioning System) technology is used to map features in a fraction of the time needed for conventional survey measurement. Other useful map layers or data products available include digital elevation models (DEM) and color aerial photography, better know as NAIP Imagery. The old reliable USGS topographic maps did not go away, they have been scanned, geographically referenced and merged into county wide mosaics for use on GIS and other less expensive mapping programs. A DEM is a digital representation of ground surface topography or terrain developed using ground sensing technology. This product provides information used in creating contour lines, digital relief maps and for spatial analysis on a GIS. NAIP (National Agriculture Imagery Program) imagery is digital aerial photography acquired by the US Department of Agriculture during the agricultural growing season in the continental U.S. High resolution color NAIP imagery is available for most areas of the U.S. and is reacquired on a periodic cycle providing a view of current conditions on the ground for updating map layers, monitoring of land use and creating astounding map images.
The capabilities of GIS provide opportunity to display map data with astonishing visual effects. By using a combination map layers, scanned USGS maps or NAIP imagery in combination with a DEM, a custom map of a particular area can be created showing a pseudo three dimensional perspective of the land. This is accomplished by laying a semi-transparent map over a shaded terrain model. The shaded terrain model creates a shadowing effect that simulates 3-D in two dimensions giving a true perspective of the ground profile. This type of map is very impressive and functional for field work, hunting or for display as a general use wall map or picture.
GIS at its highest level is a sophisticated tool designed to handle massive data sets for answering questions and solving complex problems, but at the other extreme, with the data available today, it can be used to make just a really cool map.