Precision Ag Differential GPS Exercise 
(Field Trip - Cal Poly, SLO)

Introduction: 

The purpose of this exercise is to:

• Familiarize you with the operation of various types of GPS equipment. 
• Learn how to create a simple perimeter map using GPS. This type of activity is commonly used to map fields, locate specific features such as a soil region and as a preparation for soil sampling. 
• To gain knowledge of how data is captured and transferred to GIS software. 

In the Field: 

1. Familiarize yourself with the Trimble Ag 132 and the handheld PC. 

2. With the unit turned on, answer the following: 

a) What is the HDOP? _________ 

b) How many satellites can your unit see? _____________ 

3. Using the grid sampling wizard locate the points marked in the field and take a reading at each point. IMPORTANT: The location of the GPS reading is at the antenna, be sure locate the antenna directly over the point. 

4. Set up a grid sample on a one acre grid. 

5. Navigate to the center of each grid and take a sample and record the reading. Complete the following in the computer lab. This portion of the activity will allow you to overlay the data collected by all of the groups. You should note the accuracy of the different systems and how this might influence what type of GPS equipment you use for different precision applications. 

In the Lab: 

6. Download the data from your unit into the directory given by the instructor. 

7. Start ArcView as directed by the instructor. 

8. Open the project file PA GPS.APR 

9. Create a new view 

10. Add your shape file containing the sample you took in the field 

11. Compare your data to the other points on the map. 

12. Print a map using a layout