Lab_4_Instructions

CIVE 220 1 SDSU Homework 4 Instructions Fall 2023 Civil Engineering 220 – Fall 2023 Differential GPS Due Tuesday, 10/3/23 at 9:00 pm The objective of this assignment is to apply the concept of Inverse Distance Weighting to Differential GPS. The dataset you will use is: ▪ SDSU_campus.tif – Aerial Photograph of SDSU campus Background: Survey benchmark monuments are metal disks in the ground. They measure exact horizontal positions (latitude and longitude) and/or elevations on the Earth to give surveyors points of reference. In the United States, the National Oceanic and Atmospheric Administration’s National Geodetic Survey (NGS) is responsible for managing approximately 240,000 stations established over the last two centuries. During major construction and land development, the destruction of survey monuments sometimes occurs. This destruction has increased in recent years due to rapid development. Survey markers are often used to set up a GPS receiver in a known position for use in Differential GPS surveying. 1. Obtain a GPS unit from the instructor. There are instructions for operation of the GPS units on Canvas under “Course Materials.” Use the GPS to determine x (longitude), y (latitude), and z (elevation in feet) values at three (3) known (surveyed) points and one (1) unknown point on campus: ▪ Point 1 – On sidewalk at top of stairs leading to Aztec Circle Drive near the ATM machine and coffee stand (metal disk in sidewalk). ▪ Point 2 – On sidewalk near Theater Arts building across from Love Library (metal cylinder in sidewalk 94-014). Note : This survey marker has been destroyed. Therefore, place GPS near the yellow fire hydrant in the grass next to the sidewalk. Lab #4

CIVE 220 2 SDSU Homework 4 Instructions Fall 2023 ▪ Point 3 – On curb/sidewalk next to the fire hydrant at the southeastern end of the lane between the Engineering Building and the Engineering and Interdisciplinary Sciences building (94-003). Note : This survey marker has been destroyed. Therefore, place GPS on the “fire lane” curb. ▪ Unknown Point – Statue: Samuel T. Black, First SDSU president; between Administration building and Love Library; Place GPS between his left foot & cane. 2. Create a folder named “Lab_ 4 ” in the “CIVE220” folder on your USB drive. 3. Download the mapdata zip file from Canvas to your Lab_4 folder. Extract the map data so that it can be viewed in ArcGIS Pro. 4. Open ArcGIS Pro and add your downloaded/uncompressed map data: a. Open ArcGIS Pro: Windows Start button → ArcGIS → Ar cGIS Pro b. Under “New Project,” click on “Map.” c. In the “Create a New Project” window, designate the project name (CIVE220_H4_LastName_FirstName) and location (Lab_4 folder on your USB drive) and click OK. d. Connect to the folder containing your map data: i. In the Catalog pane (on the right of the screen), expand Folders: ii. Right click on Folders and click “Add Folder Connection.” iii. In the “Add Folder Connection” dialog box, browse to your Lab_4 folder, select Lab 4 mapdata, and click OK. e. Add your map data to your map: i. In the Catalog pane, expand Lab 4 mapdata: ii. Right click on the file named “SDSU_campus .tif ” and choose “Add To Current Map.” 5. Save your Project: Project → Save Project (or Ctrl+S)

CIVE 220 4 SDSU Homework 4 Instructions Fall 2023 5. Project the GPS coordinates from GCS_WGS_1984 (Geographic Coordinate System – World Geodetic System of 1984) to SPC_NAD83 (Projected Coordinate System – State Plane Coordinates, North American Datum of 1983, meters): a. In a text box, answer the following: Is this vector or raster data? Which projection tool should you use? Why do we have to project this data? b. To project Vector Data: Analysis tab → Geoprocessing Group → Tools → in Geoprocessing pane on right side of screen, select Toolboxes → expand Data Management Tools → expand Projections and Transformations → Project . c. Name your output file the same as the input with “_SPC” appended (for State Plane Coordinates). Put the files in your Lab 4 mapdata folder on your USB drive with your other map data. ( Do NOT accept the default folder and filename. Click on the folder icon to the right of the field and browse to the correct folder.) d. For the Output Coordinate System, choose the Projected Coordinate System specified above (NAD_1983_StatePlane_California_VI_ FIPS_0406_Meters) . Click on the icon top the right of the field to select the coordinate system (Projected Coordinate System → State Plane → NAD 1983 (meters) → NAD 1983 StatePlane California VI FIPS 0406 (Meters)) e. The Geographic Transformation field will automatically populate (do not change). f. Change the size/shape/color of the symbols representing the projected points so they can be differentiated from the unprojected points. 6. Determine the x, y coordinate values for each point in meters (Refer to lab notes for additional instructions on Attribute Tables): a. Right click on the projected GPS coordinates layer (GPSpoints_SPC) and choose “Attribute Table.” b. Click on “Add” button on top of table to add a field. c. Edit the following by double clicking on the field name and either typing or selecting from the menu: ▪ Field Name – x_GPS ▪ Alias – x_GPS ▪ Data Type – “Double” ▪ Number Format – Numeric ▪ Precision (maximum total number of digits) – 10 ▪ Scale (maximum number of decimal places) – 2 ▪ After setting up all fields, right click and choose “Save” d. Add another field for y_GPS (repeat steps b and c). e. Select the GPSpoints_SPC attribute table (first tab). Calculate x values in meters as follows : Select x_GPS field, right click on field name and choose “Calculate Geometry. ” Under “Property” choose “Point x - coordinate.” For “Coordinate Format” choose “Same as input.” Repeat to calculate y-coordinate values. f. Undock the attribute table by clicking on the “GPSpoints_SPC” tab at the top and dragging it. Resize the attribute table window so that the rows and columns just fit. Take a window capture (Alt-PrtSc) and paste it into your Excel file.

CIVE 220 5 SDSU Homework 4 Instructions Fall 2023 7. Use the following information to determine your GPS error (x,y values in CA State Plane for San Diego (NAD_1983) linear units in meters; z values are ground elevation in feet above mean sea level/Geoid) : Points x (m) y (m) z (ft) Control Point 1 1,923,300.42 567,828.38 453 Control Point 2 1,922,980.17 567,806.34 436 Control Point 3 1,923,164.53 568,024.33 422 a. Enter the table above into your Excel file. Label the table as appropriate and include units. b. Create a similar table for all four points (3 known & 1 unknown) with your x, y, and z values obtained by GPS and calculated in step 6. c. What is your GPS error (in the x, y, and z directions) at each of the three control points? Assume errors are based on: ERROR GPS,i = (x, y or z) GPS,i - (x, y or z) Control,i . Calculate the errors in each direction, for each control point, in Excel. d. In a text box, answer the following: Which point has the smallest error (absolute value) in the x direction? In the y direction? In the z direction? 8. In Excel, calculate the distance in meters from the unknown point to each of the three known point using your GPS coordinates. Use the distance formula: 𝑑 = √∆? 2 + ∆? 2 9. Using Inverse Distance Weighting Squared ( with α =2 ) and the errors you measured in the x, y, and z directions for your three known points, calculate your adjusted x, y and z values at your unknown point (x*, y*, z*). Below are the sample equations for the x-direction (equations are similar for the y and z directions). Show all work in Excel. a. Weighting factor :              = = n i i i i d d w 1 2 2 1 1 where d is calculated from the distance formula b. Correction:  = = n i i x i x E w E 1 , * where x x E Control GPS i x − = , c. Adjusted x value: E x x x Unknown GPS * , * − = 10. Create a Layout View in ArcGIS Pro displaying all layers (zoomed to SDSU campus layer): a. Page orientation: Select 8.5″x11″ paper size in Landscape orientation. (Insert tab → New Layout → ANSI - Landscape Letter) b. Add a map frame. (Insert tab → Map Frame → select Map Source View). c. Insert the standard heading centered at the top (Insert tab → Graphics and Text group → Select the Rectangle Text tool). Format the font to be Tahoma, 14 pt size, and centered. (Text tab → Text Symbol group). d. Insert a North Arrow – ArcGIS North 12 – in lower left corner. e. Insert Scale Line 1 Metric with units of meters in the lower right corner (double click on the scale bar to open the Element pane and change map units). f. Move and resize elements within the layout window to best display the content. The map elements should not be within the map frame. g. Create a screen capture (PrtScr) showing your layout. Your filename (using the standard CIVE220 file naming convention) must appear at the top of your screen shot and the date and time at the bottom right. Paste the image in your Excel file. 11. Save all work and submit your Excel file on Canvas.