Lab 5 part 1

1. The advantages of using digital spatial data are that its low cost easy and quick to get a lot of spatial data and are provided in efficient forms like GPS. The disadvantages are that it is time consuming to gather data and not everything is include yet.

2. The most important question we ask our-selves when using already developed spatial-data are does it contain the information I need and is it free.

3. DOQ’s are photographic images that have been corrected for distortions due to camera tilt and terrain displacement, then georeferenced.

4. The National Hydrological Dataset is produced by the United States Geological Survey and the sources are a combination of USGS hydrologic digital line graph files and EPA reach files. The USGS files are used for spatial accuracy and the EPA files are used for attribute information. It uses North American Datum of 1983. It is a comprehensive set of digital spatial data representing the surface water of the United States using common features such as lakes, ponds, streams, rivers, canals, and oceans.
The Geospatial Data Gate way is by the United States Department of Agriculture and its source is the National Resources Conservation Service and it contains environmental and natural resources data.
The Geocommunity Data Depot is a source for SDTS format DEMs from the USGS. It also has lots of data sets downloaded from all over the Internet and is easy to access and is run by the Mindsites Group.

5. DEMs are older and need to be put together like tiles in a mosaic for large areas because they had fixed boundaries. NED provided a seamless data set in high resolution and new algorithms to remove errors created by the advancement in technology.