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?

Lab 4

1. What is an ellipsoid? How does an ellipsoid differ from a sphere?

        An ellipsoid is a manipulated ellipse based on the region being projected. In essence, an ellipsoid is a sphere with flattened poles, and is considered much more accurate in mapping the earth.

2. What is the imaginary network of intersecting latitude and longitude lines on the earth's surface called?
  
        Graticules

3. How does the magnetic north differ from the geographic North Pole?

        The magnetic north pole is where compasses point to on earth whereas a geographic north pole is the pole on which the earth's axis rotates. They are not the same point.

4. Why are datums important? Briefly describe how datums are developed.

        Datums serve as a reference for ellipsoids and geographical accuracy. They are composed of a specific ellipsoid and specific points on the earth that specify the surface of the earth.

5. What is a map projection?

        A map projection is when the 3-dimensional surface of the earth is projected onto a 2-dimensional mapping area.

6. What is a developable surface?

        Developable surfaces are geometric surfaces in which the earth can be projected onto. Some examples include cones, cylinders, and planes.

7. Which lines on the graticule run north-south, converge at the poles, and mark angular distance east and west of the prime meridian?

a. Lines of longitude

8. Which of the following ellipsoids is now regarded as the best model of the earth for the region of North America?

c. GRS80

9. Which well known coordinate system would be appropriate to use for developing and analyzing spatial data when mapping counties or larger areas? Why?

        The state plane coordinate system would be best due to the fact that it increases in accuracy over larger and wider distances.

10. What is a great circle distance?

        It is the distance between two points on the earth via the earth's curvature.


A map projection is the building block of the major 2D maps that we all use on a daily basis. They come in all types of forms, projected onto different shapes (circles, cylinders, planes) depending on the type of map being created and its purpose. A map projection's significance lies in its determining how accurate a map can be.

The type of projection one uses depends solely on what type of purpose the map is going to achieve. No matter which type of projection is used, there is always distortion to some extent, as the irregular shape of the earth cannot be 100% fully illustrated on a 2D surface. Thus, different types of projections were created.

The equidistant maps I used were the Sinusoidal and Platte Carree projections. The Sinusoidal map shrinks at the poles, in an attempt to sort of mimic the spherical shape of the earth, though the distortion is heavy at the poles. The Platte Caree projection equally spaces all meridians on the globe, making the higher latitudes wider than they actually are.

For my conformal maps, the Mercator exaggerates the sheer sizes of Greenland and Antarctica, making Greenland almost as big as North America! The Fall Stereographic is similar, but distortion at the poles is much less drastic. For these types of maps, only areas around the equator are visually accurate.

For the Equal Area maps, though the Bonne and Mollweide both encompass the same area, the Bonne's extreme bending of the poles actually brings Baghdad and DC closer together, in contraste with Mollweide.

Lab 3: Data Formats and Models

1. What is a data model? Describe the two most commonly used data models.
 
      A data model is a model that illustrates a part of earth on a GIS. The two most common data models are Vector and Raster.

2. What is topology and why is it important?

          Topology is the relationship between points and lines on a data model. The main difference between it and the spaghetti model is that topology maintains relationships even with molding.

3. What type of data model would be best for representing hillside slope? Justify your answer.
 
      Raster, because the grids in raster maps are better suited for elevation than lines on a Vector data model.

4. Describe the relationship between spatial detail and cell dimension with regard to raster models.

       The less cells available, the less spatial detail is illustrated. In retrospect, small, abundant cells provide more spatial detail.

5. What are the four types of attribute data? Give an example of each.
  
          Nominal - place name
          Ordinal - ranking of nominal data
          Interval - temperature
          Ratio - sea depth

6. List two types of vector data file formats.
    
   .shp & .eOO

7. List two types of raster data file formats.

       .img & .TIFF

8. You can do all of the following in ArcCatalog EXCEPT:
 
      c. Select features

9. In the Chapter 4 exercises, does the World.mdb geodatabase contain a feature dataset?
    
      yup

10. What are the names of the feature classes contained in the World.mdb geodatabase?
 
      cities, countries, disapp_area, world30

11. What data format does the flight_path.lyr layer file reference?
  
     .shp

12. What are two ways to add data to an ArcMap document?
 
          1. Click on the (+) Add Data button
          2. Drag and drop from ArcCatalog

13. How many features (records) exist in the dissap_area feature class?
  
      699!

III. Complete the ESRI online module “Basics of the Geodatabase Data Model” and
post a screenshot of the certificate.

Lab 2: ArcGIS and ArcMap

1. What types of software products are included in ArcGIS and which one will we be

using most in this course?

 

       ArcGIS includes Desktop GIS, Server GIS, Mobile GIS, and Online GIS. We will be focusing mainly on Desktop GIS in this course, particularly ArcMap.

2. Would it be better to perform most of your data analysis and layer symbolization in

data or layout view? Why?

      It would be best to do it in layout view since it enables you to physically observe the data trends more than in data view.

3. What are two ways to obtain help for ArcGIS Desktop?

     Help > What's This? or Shift + F1

4. How are attributes linked to geographic features?

     They're linked in an attribute table via a "unique identifier"

5. What is the file extension of an ArcMap document?

     '.mxd' aka a 'map document' 

6. What are two ways to zoom in/zoom out on a map?

     View > Layout Zoom, View > Data Zoom 

7. List three operations available in the ‘context menu’ of a layer. Hint: Right‐clicking

with your mouse in the TOC should help you with this question.

     Label, Open attribute table, and Zoom 

8. If the check box next to a layer in the table of contents is grayed‐out, what does this

mean? How would you resolve this issue?

     If it's grayed out, it means you haven't saved the data into your file, therefore it is not able to access the data. 

9. What are the differences between large and small scale maps? Provide an example of

each.

     Large Scale = more magnification/bigger fraction. Example: map of Northridge

     Smalle Scale = less magnification/smaller fraction. Example: map of Russia

10. Describe the differences between features and surfaces. Provide an example for each.

     Features are specific points in a map, such as a city marking or a river marking. Surfaces are smooth, broad parts of a map, such as a lake or body of water.

11. A GIS is a useful problem‐solving tool. You can do all of the following tasks with it,

except one. Which one?

  

   a. Create project criteria

12. What are the minimum and maximum elevations of the cities Earhart visited? Briefly

describe how you determined these values.

     Minimum elevation visited: Sea Level, Maximum: 1045ft. Found in attribute table under elevation.

13. On the continent of Africa, what is the approximate distance (in miles) from Dakar to

Assab? What are two techniques (one tool and one process) you could use to figure

this out?

     4,016 miles (approximately). The measure tool can be used or referring to an existing attribute table of African cities and distance between them. 

14. What are two possible methods you could use to figure out the names of the cities

shown on the map?

     Identify > Click on city, or open up the layers to see how it's labeled.

15. Zoom to the extent of North and South America so that all the cities Earhart visited are

labeled. Capture a screen shot (Alt + PrtScr) of this view and paste into your Word

document (Ctrl+v). Turn in this screen shot with your answers from this sheet.

      (Unable to paste screenshot into blog...)