Project 3
Finding, Retrieving, and Viewing National Map Data
Matthew Calamito
Digital Elevation Model (DEM)
The image pictured above is a Digital Elevation Model (DEM) of my hometown of Frenchtown located in Hunterdon County, New Jersey. This DEM of Frenchtown roughly covers 60 square miles. I was able to acquire this data from the Geocomm site at http://data.geocomm.com/dem/demdownload.html. This Digital Elevation Model has a resolution of 1:24,000 (10m). When I retrieved the data from the Geocomm site, I had to put it into a program called Global Mapper. This enabled me to put the quantitative data into a visual model as shown above.
My hometown, as you can see, is filled with streams and creeks and in certain areas elevations are higher than others. The big blue feature represents the Delaware River. Many of the streams and creeks distribute their water and run into the Delaware. The higher elevation in my hometown is represented by the dark yellow and red colors in the Northern region of the model. There is a lower elevation closer to the river and this land is much more flat where most residents reside.
Digital Line Graphs (DLG)
Imaged above is a Digital Line Graph (DLG) of my hometown of Frenchtown, New Jersey. The area covered is once again about 60 square miles, which is the same are covered by the previous DEM. I was able to obtain this Digital Line Graph through the Geocomm website at http://data.geocomm.com/dem/demdownload.html. With the help of this website I was able to acquire three types of files; boundaries, hydrography, and hypsography. After I obtained these data files, I used the Global Mapper program once again. This program transferred that data into a visual DLG map. Since the map is quite confusing to look at, the summary of what each of the colors and symbols mean might be helpful.
To start off, the boundaries are represented by the light brown/grey lines. These boundaries separate the townships in my home area. Hydrography are represented by the blue lines, some thicker than others. The more thin lines are equivalent to creeks and streams, and the thicker ones represent rivers. The big thick blue line at the bottom left corner is the Delaware River. You can see a DEM and a DOQQ representation of the Delaware River as well by looking at the correspondent pictures above and below this DLG model. Lastly, the brown lines stand for the hypsography (surface contours). The dark green triangles give the peak elevation marks at certain points of interests. The closer that the brown lines are, the more steep the distance is between them. As you can see, my hometown has many high and low elevation points along with many creeks and streams.
Digital Orthophoto Quarter Quadrangle (DOQQ)
The image pictured above is a Digital Orthophoto Quarter Quadrangle (DOQQ) of my hometown of Frenchtown, New Jersey. The area covered by this DOQQ is 3' 45'' from North-South (40o33'45''-40o37'30'') and 3' 45'' from West-East (75o03'45''-75o07'30''). I was able to acquire both the data and the photo from the USGS EarthExplorer Data Collection Set website at http://edcsns17.cr.usgs.gov/EarthExplorer/. This helped me out a lot because I didn’t have to use any type of program or software to convert the data into a map. This website allowed me to do it all on the site. The DOQQ photograph was taken on April 13, 1999 which means that it is only around 6 years old.
However, within those six years many things have changed. There is still a lot of farmland as you can tell by the open space. These are the many farming fields, but some of them have been developed since this photograph was taken. The river running along the bottom left hand corner is once again the Delaware River. This rural area is where I have spent most of my life and it is really interesting to be able to see my hometown from an aerial photograph. My house is located on the left side of the photograph in the middle where the smaller groups of houses exist. It’s a neat experience to be able to see all the roads that I drove on and all the places I’ve been in my hometown just by looking at this map. I can also see just how developed my town has gotten in six years and I'll be excited to see the next DOQQ of Frenchtown to be able to compare the two hand in hand.
A Taste of Knowledge
A type of photography that many geographers use is called Aerial Photography. This example of photography is broken down into two parts, vertical aerial photography and oblique aerial photography. The difference between the two is that vertical is taken above straight down onto the area and oblique is taken above from an angle onto the area. Below are examples of vertical aerial photography and oblique aerial photography.
Oblique Aerial Photograph
rockyweb.cr.usgs.gov/.../ virtour/fedcen4.htm
Vertical Aerial Photograph
rockyweb.cr.usgs.gov/.../ virtour/fedcen5.htm
Geographers often use Aerial Photography when making topographical maps. The type they use is vertical aerial photography. On a vertical photograph, the position directly below the camera, or the principle point, is the only true point on the photograph. By overlapping the vertical aerial photographs along the geographer’s flight path, topographical maps can be made.
Sources
Earth Explorer. Internet. Online. 23 October 2005. http://edcsns17.cr.usgs.gov/EarthExplorer/.
Geocomm. Internet. Online. 23 October 2005. http://data.geocomm.com/dem/demdownload.html.
United States Geological Survey (2002) dlgv32 Pro Viewing Software. http://mcmcweb.er.usgs.gov/drc/dlgv32pro/ Accessed 24 August 2002. Note: dlgv32 Pro software is installed in the Geography Instructional Computing Laboratory in Room 208 Walker Building.
United States Geological Survey (2002) Geographic Names Information System. http://geonames.usgs.gov Accessed 25 October 2005.
United States Geological Survey (2002) USGS Geographic Data Download. http://edc.usgs.gov/geodata/ Accessed 25 October 2005.