Name NRS 509 Exam I. Right Map

Transcription

1 Read every question carefully. You may use a calculator if you wish. Conversion tables are provided at the end of the exam. If you have any questions, raise your hand. Be sure to show your work on computational questions. Pace yourself, you have 75 minutes to complete this test. 1. (10 Points) Consider the two maps of the Chipuxet aquifer (gray blob) next to the URI campus below. For each map, measure the width of the aquifer using (1) the scale bar and (2) the scale ratio. Report your measurements in kilometer ground units. Which map is flawed? How can you tell? What do you think the source of the problem is? Left Map scale using scale ratio: 80000*1.625 = =3.3km scale by scale bar = 3.3km Right Map scale using scale ratio: 80000*1 =80000 =2.0 km scale by scale bar = 3.2km Right map is flawed, major difference in scale bar and scale ratio. Map was reduced in size but scale ratio stayed the same. Page 1 Points Total Points this page = 10

2 2. (12 Points). Map Accuracy. A. Usually, large scale maps are more accurate than small scale maps. You have two sources of stream locations in your GIS database (and both meet National Map Accuracy Standards). One was mapped at 1:24,000 scale and the other was mapped at 1:15,000 scale. Which one has the best spatial accuracy? Is this an example of large scale maps being more accurate than small scale maps? Why or why not? S= 24,000 S=15,000 Md=0.02 Md= Gd= 480 Gd=500 More accurate Less accurate Difference due to 1:20,000 threshold in NMAS tolerance from 1/50 th to 1/30 th B. I am using an old NOAA nautical chart of Rhode Island that is mapped at a scale of 1:500,000. It meets National Map Accuracy Standards. The problem is, the chart is in NAD27. All my other data are in NAD83. What is the positional accuracy of shoreline (expressed in feet on the ground) on this map based on National Map Accuracy standards. What is the difference in a shoreline in NAD27 and a shoreline in NAD83? Express your difference in inches on the map itself. S=500,000 Md=0.02 Gd=Md*S=500000*0.02=10,000 =833.3 NAD 27 / NAD 83 difference = 50 m in RI 50 m = Gd= S=500,000 Md=Gd/S=1968.5/500000=0.004 This is less than ½ a pen width and probably invisible to the naked eye. Don t worry about NAD difference 3. (24 Points) Consider the following questions concerning standard data for GIS systems. When identifying or describing a dataset, include the source agency, the resolution of the dataset (or pixel size), and the format (raster/vector). A. What is the NLCD dataset and what would you use it for? National Land Cover Data, USGS, national land use and land cover. Many viable applications, 30 m pixel, raster Page 2 Total Points Points this page = 16

3 B. If you were modeling risk of inundation from sea level rise for a small area in downtown Providence, what would be your best source of downloadable elevation data from USGS? Be sure to tell me what resolution you would use. 1/9 arc second (3 m) NED, USGS, raster C. If you were modeling landslide risk zones (based on steep slopes) for Portugal, what would be your best source of downloadable elevation data from USGS? Be sure to tell me what resolution these data would be in. SRTM, 90 m pixel, USGS, raster D. What resolution of census data would you use if you wanted to make a highly detailed map of the spatial pattern of where senior citizens live in downtown Providence? Block level TIGER polygon data from Census Dept., vector, 1:24,000 E. What dataset would you use to determine the exact location of 12 specific streams in Rhode Island for which you had water quality and pollution data from EPA for the 12 stream segments. NHD, 1:24,000, USGS, vector F. You need to map soil drainage classes for your town (in RI) in order to determine where septic systems might fail. USDA NRCS SSURGO, 1:15,840, vector Page 3 Total Points Points this page = 20

4 4. (10 Points). An early choice you must make in performing a GIS analysis is choosing the proper format of the spatial data you intend to use. Please answer the following questions concerning raster and vector GIS data. A. Name two common geospatial datasets that come from federal sources that originate in raster format. For each, provide the name of the dataset, the agency that distributes it, what the data represent, and the pixel size of the dataset. NLCD, 30 m, USGS NED, varies from 30-3 m, USGS SRTM, 90 m, USGS DRG, 1:24K, USGS DOQ, 12K, USGS B. Describe a situation where a raster GIS data model would be the most appropriate data model for a GIS application. When you start with a raster dataset for example NLCD, or you have a lot of modeling to do. Many possible correct answers. C. Describe a situation where a vector GIS data model would be the most appropriate data model. Atlas quality mapping, need topology. Many possible correct answers. D. Describe a situation where either a raster or a vector GIS data model would be equally appropriate. Some analytical procedures, when you can convert from one to another, when you need atlas quality maps and your pixel sizes are very small. Many possible correct answers. Page 4 Total Points Points this page = 10

5 5. (10 Points). A GIS is much more than computer software and data files. A. What are the five elements of a complete, integrated GIS system? What element is the cheapest? What element do you think is the most expensive? People, methods, hardware, software, data. People most expensive, data might be cheapest now. B. How about geospatial data -- what are four unique properties of this kind of information? Briefly define or describe each one of these essential components of geospatial data. Graphic Element -- points, lines, polygons, pixels Attribute/Database Element -- database defining features Geographic Parameters -- NAD, coordinate system, projection Topology -- adjacency, connectedness Metadata -- data about data Partial credit given for other logical answers Page 5 Points this page = 10 Total Points

6 6. (16 Points) Consider the map below. What is the scale of the map? The asterix (in the north) is RI State Plane (feet) coordinate , The dot is RI State Plane , Gd= =111,000 =1,332,000 Md=1.5 S=1,332,000 /1.5=888,000 1 : 888,000 Using this scale, what is the distance in kilometers from the cross to the star? Md=1.5 S=1:888,000 Gd=1.5*888000=1,332,000 = 33.8 km Page 6 Total Points Points this page = 8

7 If the UTM coordinate for Kingston (cross) is 300,000 W and 4,596,000 N, what is the UTM coordinate for the center of Block Island (island off the south shore of the state, you can assume is exactly south of Kingston). Use the scale you determined for this map in making your estimate. Md = S= Gd=Md*S=888000*1.376=1,221,888 = 31,036 m 4,596,000-31,036=4,564,964 Coordinate is 300,000 by 4,564,964 An emergency airlift medical helicopter located at the asterix in northern RI has received a call for help from the middle of Block Island. The helicopter carries enough fuel for a 120 mile trip. Can the helicopter make it to Block Island and back? Use the scale you calculated in the first part of this question to determine the answer. Show your calculations. S = Md=3.5 Gd=Md*S=888000*3.5=3,108,000 =49 miles one way Round trip = 98 miles. OK to make the trip 7. (18 Points) Short Answer. Provide a brief description or definition for the following terms. Aerial photo versus orthophoto Air photo has distortion from tilt, optics, and terrain. Ortho have these error removed. NAD 27 North American Datum Early frame of reference for positioning. Meades Ranch Kansas. Replaced by NAD83 Web Map Service Digital image (jpg) of map scene streamed to display from server. No data, no ability to control symbology Topology Spatial relationships, connectedness, embededness, adjacency Page 7 Total Points Points this page = 20

8 73.14 W, N Decimal degree coordinate of Lat/Lon ESI Environmental sensitivity index, NOAA dataset on coastal features used in emergency response. Page 8 Total Points Points this page = 6