Field Activity 4

INTRODUCTION:
Surveying is the act of taking a collection of points to make some kind of reference, map, or image.  Surveying is just a type of sampling that can be done in a number of ways.  The three most common types of sampling are random and systematic.  A random sample method is just that.  The points measured have to be completely random.  This can be done with a random number generator or a coin toss.  Systematic approach is using a pattern.  This would be  These methods can be very useful in getting measurements of data especially in spatial situations.  These sampling points are supposed to be snapshots to give you an idea of what the rest of the landscape would look like.  The objective of this lab was to create a landscape and using a simple surveying or sampling method, collect the elevation changes in this small area.

METHODS:
Group 6 chose to sample every point in the grid pattern.  (Figure 1)  The box is 114cm x 114cm.  This was divided up into 19 6cm squares.  Then elevation values were taken at each point in the grid pattern.  A total of 400 data points were collected.  Sea level was the top of the box.  In this case this land would flood very easily because it was below sea level in most points.  Instead of a systematic approach a measurement was taken at every cross of the grid.  This gave the information needed to make a 3D map (X,Y,Z)  Tacks were used to hold the points and string was strung across the sandbox.  This created the grid pattern.  The 6cm squares allow for very high precision.  The points were collected with a ruler and transferred into an excel file.  This data will allow easy access and creating a feature class.

Figure 1:  This image shows the grid pattern that was used to collect the data points.

Figure one shows that the origin (0,0) point was in the top left of this image.  Moving to the right in the image, the valley is the first feature.  The middle of this area is dominated by a plateau landform while there are two small hills in the bottom left corner.  A ridge runs from the hill and down into a depression on the bottom right of this image.  

RESULTS:

400 sample points X,Y,Z values were recorded.  There was not much difference in the elevation.  The lowest point recorded was -6cm while the highest value recorded was 4cm above sea level.  This makes the range a difference of 10.  The most frequent value recorded was -2cm below sea level.  Since all points were collected, the data gathered should be extremely accurate.  This method should met the objective better than any of the other sampling methods.  This method would not be practical on a much bigger scale.  The group stuck to the original plan.  It did take a while to figure out what kind of plan and direction we wanted to go.  A numbering system would have made collecting the dat points go much faster.

CONCLUSION:

This sampling method is extremely accurate but also very time consuming.  In spatial situations this can be effective for mapping.  These sampling methods can cover larger areas in less time.  This would make the map a little less effective.  The survey did a great job showing the numbers that were needed.