Monday, February 25: Land Navigation Maps

Introduction:

     This week is going to be a short post; much as how on the 18th I provided only the first half of an exercise (which has yet to be completed, we'll get there eventually!) this week's project was more preparation and less completion.  The ultimate goal for this week is to prepare for next Monday when we will be working in the field, conducting a survey of the "Children's Nature Academy," also known as the Priory and a recent acquisition of the University's.  The property contains over one hundred acres of former monastery lands: three buildings containing over 80,000 square feet, and plenty of wooded lands just past the outskirts of Eau Claire.  In preparation for this survey, we are going to do two things: find our individual pace count and develop a navigation map.  This week, we will be grouped in threes: my partners are Joey and Brandon (both of whom keeps a very nice blog as well, by the way).

fig 1  St. Bede's upon acquisition

Methodology:

     The first item to get out of the way is the pace count.  Professor Hupy informs us that we will be needing this count for next week, so some dead reckoning is to be expected in our navigation.  The entire class paced out 100 meters on flat terrain four times to determine how many paces each individual has in that distance (this is a standard pace count).  One pace is every other step, starting on the left foot every right step would be counted.  These steps are supposed to be casual, like one would do when hiking.  My first set was 67 paces, followed by three sets of 61 paces so I'm going to call my count 61.  When in the field, I will have to estimate (or guesstimate) how the terrian is affecting my step size to figure what difference it may make in my pace count and keep me from getting lost in a one hundred acre wood.  For such a small and simple task, this step is perhaps more important to do correctly than the making of the map; a bad map may still be workable on a small scale if you are able to calibrate distance correctly, but the opposite is not true.  If I get lost, I intend on using the serene sounds of the nearby interstate to guide me towards civilization, but if there's no traffic and I get lost then there will be a problem.



fig 2  The UWEC Campus, the Priory is in the lower left, quite away from the rest of campus.



fig 4 What happens to those who do NOT know
how far they've travelled

fig 3 What happens to those who know
how far they've travelled

 

     With pace counts in hand, it is time to develop a navigation map that will be used in the field.  A good deal of data was provided by the Professor Hupy and our talented Geospatial Facilitator Martin Goettl: aerial imagery of the area in both color and black and white, topographic data contour AutoCADs at both 2m and 5m intervals, a DEM (see my second post), an actual USGS topo map (Digital Raster Graphic, DRG), and boundaries for both the navigation area and the point area.  The topographic countours were developed from a the DEM which was downloaded from the USGS seamless server, and the DRG image came from the same place.  The ramaining data was developed for a UWEC survey.
     Our final product needs to be a pair of 11x17 maps projected into UTM (Zone 15N) that are going to guide our navigation through the wilderness with a grid overlay; we are free to include whatever data we feel whatever will be useful.  The maps also must contain the data sources and projections being used.  For a project like this, it was decided that UTM would be the most valueable projection because of the low distortion although a county system might have been more precise, because UTM coordinates are easy to understand and universal.  Unprojected coordinate systems (latitude-longitude) are So the first trick is to project all of our data into UTM as to ensure that it matches for the map.
     Most of the data was already in UTM, however the AutoCad topographic contours at the 2-m interval were neither in UTM nor was their projection defined when we recieved the data, so when ArcMap attempted to lay it on top of the other datasets already laid out it was unsuccesful (figs 5 and 6).  Thus began the process of discovery that can be working with a data set sans metadata.



figs 5+6 or Projection: you're doing it wrong. The top image is the 2m contour, the bottom is our USGS topo with 5ft contours in red. Notice the highlighted coordinates, and how they don't match by roughtly forty degrees longitude. This will have to be remedied.

     To solve this problem, we needed to determine the original projection of the data and define it so that it could be projected by the software.  There are several ways to accomplish this task, myself and at least one other classmate attempted to guess the appropriate definition a few times until we got lucky, which actually worked when Beatriz tried the Wisconsin Tranverse Mercator and our contours fell right into place.   This makes sense, since WTM is the state system projection for Wisconsin, a good choice for USGS topographical data. Of course, guesswork is never professional, so although the data looks good and may work for personal purposes it is still useless until it can be shown that this is indeed the projection that the data was imported in.  This can be solved by either re-loading the data ourselves or asking the data provider(s), in this case USGS or Martin.  Martin, having an office across the hall and being immediately available, was willing to find the original download and found that in fact the data did arrive in Wisconsin TM.

fig 7 or Projection: you're doing it right. Notice how all those lovely blue 2-ft contours line up with the topographic raster? You may need to expand the image. Also, does this map seem busy to you?

     Now that all of the data is in one projection, all that remains to accomplish this week is a little cartography!  Being that we get to use both the front and back of our paper for our maps, our group decided it would be wise to use one map that would be easy to mark as we comducted our survey and one map that showed the terrain in more detail.  The main concerns with creating each map were 1) can we use it to navigate and 2) can we use it to navigate.  The maps need to be readable and not too busy or cluttered to use.  The maps also need to give an adequate idea of the terrain at a given point, and the best maps will balance both.  Fortunately, the ability to have two maps sidesteps the problem somewhat by allowing us to split the information across two maps.
     I created a pair of maps for the excersize, the first was a combination of the color aerial photograph and the DEM (fig 8).  I chose the color aerial instead of the black and white one because it was taken in the autumn and the difference between evergreen and deciduous forest is very clear on it when compared with the black and white.  The digital elevation model was layered underneath a 25% transperent aerial, both rasters had the contrast beefed up 20% as to be more defined.  I could not decide whether to add the 2m contours, because the DEM still did not give a well enough defined idea of slope over the study area for my taste but adding it made the map far too busy and the 5m contour was not useful at all in this regard becasue the spacing is higher than I like.  I settled on adding it but clipped them to the area of interest and turned on the transperency so that the contours don't overwhelm the aerial and DEM.  Overlaying the entire output is a grid of the UTM coordinates at 50 meter intervals to assist with navigation.  I also added a single full color aerial.

fig 8: My Aerial Map. 









     I also created a much simpler map of just the contours with an extremely light DEM underneath for a tiny bit of added clarity. This map is pretty straightforaward (fig 9), I must give credit to Joey for the format of the legend, North Arrow, scale bar etc. as he had already completed his map by this time and I both liked the sharpness of his layout and I wanted to acheive consistency if we were to print maps from different group members.  To make it look nice.

fig 9: My Contour Map

Discussion:

     In the end, our group sent in one aerial image and one 2ft contour map with a light DEM in the background.  The grids we used were at_____ intervals... more soon...like an image of what we sent in...