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?

Advantages are readily accessible and can be use in various projects by various entities.  Directly transferred to other digital devices.  Disadvantages include different formats of data stored, inaccurate data and outdated data being used.

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

Is this data relevant and up todate

3. How do DOQs differ from regular photographs?

Scanned aerial photographic images that have been corrected for distortions due to camera tilt and terrain displacement, and then are georeferenced

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

·         Digital Raster Graphic (DRG)-

·         Georeferenced raster image of a scanned USGS map

·         Usually 1:24,000 scale in the US

·         Stored in geotiff format (*.tif). Used for quick check for consistency in data collection and for navigation when displaying data.

·         Digital Line Graphs (DLG)-

·          Vector representations of features displayed on a USGS national series map often in SDTS format.

·         Provide a limited set of attribute information and are highly structured to convey topological relationships

·         Digital Elevation Models (DEMs)-

·         Elevation data in raster format

·         Created from ground and aerial surveys of original elevation measurements

·         Spatial resolution of 30 meters (often 10 meters)

·         USGS National Elevation Datasets –Primary delivery as a seamless data source.

·         Created for specific projects such as road construction

5. What is the difference between DEMs and NEDs?

NEDs provide higher resolution images for larger areas with greater accuracy.

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

a. What are the names of the feature datasets in the geodatabase?

Base map and hydrology

b. What are the names of the feature classes in the hydrology dataset?

NHDFlowline, NHDPoint, NHDWaterbody, Watersheds

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?

SHP

c. Is there metadata associated with topoq24.shp?

yes

d. What is the GIS data format of the NHDFlowline layer?

ArcGIS Geodatabase

e. Is there metadata associated with NHDFlowline?

yes

f. What are 3 keywords used to describe the NHDFlowline layer?

FWHYDROGRAPHY, Hydrography, Stream / River

g. Who created the NHDFlowline layer?

Earth Science Information Center, U.S. Geological Survey

4. Export the NHDFlowline feature class to a shapefile format, name it NHDFlowline.shp and place in the Lab_5 folder on your C-drive.

a. Is there still metadata associated with the layer?

Yes there is

b. In the USGS_QD_ID field, find the value that corresponds to the Canoga Park QUAD_NAME. What is it? _34118-B5______

7. Load the DOQQ tiff into your Lab5 ArcMap document. Is the DOQQ black and white or CIR (color infrared)?

Black and white

8. Use the DOQQ and Highways layer to find the CSUN campus. Zoom to that location. Capture a screenshot (Alt+PrintScreen) and paste into a Word document with your other answers for this assignment.

9. Save your Lab5.mxd document and close ArcMap.

10. In ArcCatalog, navigate to your Lab5 folder. Capture a screenshot (Alt+PrintScreen) of the expanded folder/file structure and paste into a Word document.

12. Open the Lab5.mxd document again.

a. What happened to the lacounty_lu01.shp layer?

The La county disappeared