Lab 5

I. Answer the following questions based on Bolstad Chapter 7 and lecture. 1. What are some advantages and disadvantages of using digital spatial data?

Digital Spatial Data is very efficient, readily-available, and by far the quickest source for data. A disdvantage to using it would be its less accurate sources (in some cases). Because it is so easily obtained, it can also be easily made by unreliable sources.

2. What are the most important questions you must ask before using already-developed spatial data?

You have to make sure that the source of the data is reliable, make sure that the projection is the type you wish to use, and make sure the data itself is the exact data you are seeking.

3. How do DOQs differ from regular photographs?

DOQs have removed displacement caused by terrain relief and camera tilts – thus, a more accurate “aerial photograph”

4. Choose three existing data sets and describe who produces them, what the source materials are and what they contain.

The NED (National Elevation Dataset) is produced by the USGS and uses aerial surveying.

Alabama DOQQ County Mosaics – a DOQQ dataset produced by the USGS and also uses aerial surveying.

Texas CLU bundle is a dataset also prodocued by the USGS that contains roads and calculated acreage of land in Texas.

5. What is the difference between DEMs and NEDs?

NEDs are produced by the USGS and is general elevation data that is the best raster data available of the US. NEDs are made up of DEMs, which are raster maps of specific relief areas.

 II. Step through the following instructions and answer any associated questions.

Basemap and Hydrology

b. What are the names of the feature classes in the hydrology dataset? c. For each one of the feature classes you just listed, describe whether it is a polygon, line or point layer.

NHDFlowline - Line
NHDPoint - Point
NHDWaterbody - Polygon
Watersheds - Polygon

3. Using ArcCatalog, answer the following questions.
a. Is topoq24.shp a raster or vector layer?

Vector

b. What is the GIS data format of topoq24.shp?

It’s a shapefile



It is vector data.
YES

e. Is there metadata associated with NHDFlowline?



g. Who created the NHDFlowline layer?
Yes
'US Geological Survey in cooperation with US EPA, USDA Forest Service, and other Federal, State and local partners'
a. Is there still metadata associated with the layer? River, Lake / Pond, Canal / Ditch, Reservoir, Springf. What are 3 keywords used to describe the NHDFlowline layer? d. What is the GIS data format of the NHDFlowline layer? c. Is there metadata associated with topoq24.shp?
noa. What are the names of the feature datasets in the geodatabase?