Lab IIX: Preface;
Ground Truth Data for the LIDAR Lab
Updated 3/2/2010
Outline of Document
(Click on links to jump to a section below):
Garmin GPSmap60-C Basic Operation
Garmin
GPSmap60-C Create Waypoint (Ground Truth Site)
Garmin
GPSmap60-C Data Download
Add Coordinates to Attribute Table
What if can't get my data to download from the
Garmin?
Introduction; Ground Truth Data: Prior to taking on our LIDAR Exercise, we will need to collect some additional ground truth data. As discussed in class, we will begin by heading out to Sehome Hill to collect some field data using the Point-centered Quarter method. More information that you’d ever want to know about this method is available here: PCQM.pdf
You should print out a copy of the data sheet to take out into the field with you (tree_data_entry_table.xls.).
The basic idea behind PCQ sampling is quite simple. You randomly select a point in the forest. Using a compass, you divide the area around this point into four quadrants (northeast, southeast, southwest, northwest). Within each quadrant, you then locate the tree that is nearest to the point center. For this tree, you then record three pieces of information:
1. Distance to the tree in meters
2. Diameter of the tree at breast height (DBH) in centimenters. Note that “breast height” is defined as 1.37m above the ground on the uphill side of the tree. Note that, in order to be counted, a tree must be at least 10 cm DBH at 1.37m above the ground.
3. Species of the tree.
At each point, this means that you will be recording data for only FOUR trees. The arrangement might look something like this;
In our case we want to collect data for clusters of four points. You will randomly select a “Plot center” and collect PCQ data for four points that are locate 5 meters north, south, east and west of this plot center. Like this:
It is critical that you use a compass and tape measure to accurately lay out the position of each point relative to the plot center. As indicated in this figure, you will use a GPS unit to log a waypoint for the plot center. See the below for instructions on how to do this using the Garmin GPSmap60 units. Note that you will need to set the unit to AVERAGE MULTIPLE POSTIONS to increase your accuracy. THIS IS CRITICAL! The coordinates for our ground truth points will need to be accurate to within a meter or two! Unlike our previous labs, we will be using the NAD83 datum, not the NAD27 datum. You should record the coordinates of your plot center in the field. Recall that this is an instantaneous position. You will be using the download instructions below to download the far more accurate averaged position. You can use the position that you recorded in the field for a reality check and as a backup in case you run into problems with the download.
At each Plot, you will record data for SIXTEEN trees. Like this:
Try to collect data for as many plots as you can. The more data we have the better. When you get back to the lab, enter your data into this datasheet: tree_data_entry_table.xls. See the instructions below on downloading your GPS position. These are essentially the same as in the previous lab except you will be working with the NAD83 datum rather than NAD27 as in the previous lab.
The Study Area: The study area for this lab is the Sehome Hill Arboretum. Confine your sampling to the forested areas and try to get at least one plot in a conifer-dominated site and at least one in a site dominated by deciduous trees. I would encourage you to work with at least one partner.
Garmin GPSmap60: Although you can make the Garmins display coordinates in UTM NAD83 (or NAD27), these coordinates are actually stored and download using the WGS84 datum. This means that, back in the lab, we will need to convert your coordinates from WGS84 to UTM NAD83 (more on this below).
Basic Operations For the Garmin GPSmap60-C GPS Receiver
(These instructions are modified from a document prepared by Stefan
Freelan: J:\saldata\tut_GPS\Garmin_GPSmap60\3_GPSmap60_howto.doc)
Turn Unit On - Press & hold Power button (top of unit next to antenna)
-
Unit comes on and searches for satellites (wait…)
-
Opens to Satellite screen with the Location and
Accuracy
Estimate at the of the screen
Turn Unit Off - Press and hold the Power button
(top of unit)
Switch Screens - Press Page
button (on right side) to switch between the
5
Main GPSmap60 Screens:
Satellite
– skyplot of satellites & satellite strength
Trip
Computer – Info on speed, bearing, ETA, etc.
Map
– w/waypoints & cities, can pan/zoom
Compass
– w/info on speed, ETA, etc.
Main
Menu – settings, manage tracks, etc.
*
Note: the GPSmap60-CS also has an Altimeter screen
Navigating within the GPSmap60
Screens and Selecting Items
- Use the Rocker Button
(large, center button w/arrows)
to
“navigate” Up-Down-Left-Right to highlight items
-
Press ENTR (Enter) button to select a
highlighted item
Zoom In/Out (on the Map screen)
-
Use the OUT button (upper right) to Zoom Out
-
Use the IN button (upper left) to Zoom In
Backlight On/Off - With unit
on, press Power button (top) once briefly
- Use Rocker
button to adjust up/down as desired
- Backlight goes
off in 15 seconds (or press ENTR)
Change Units (Note that this step is
critical!!!)
- Main Menu screen
-
Select Setup, select Units
-
Adjust Position Format to: UTM
UPS
-
Adjust Map Datum to: NAD83 CONUS
- Adjust Distance to: Meters
Time of Day - Bottom of Main Menu screen
Check Battery - Top of any screen
Set Battery Type - Main Menu
screen – Select Setup – Select System
-
Under Battery Type, choose either:
Alkaline (disposable) or
NiMH (Nickel Metal Hydride – Rechargeable)
Change Battery - Lift metal loop on back of unit
-
Turn loop counterclockwise 1/4 turn
-
Remove back cover, replace batteries (2 AA)
-
Replace cover, turn loop clockwise 1/4 turn and fold flat
* * * Turn Unit OFF when not in use
to save battery * * *
Press Mark button, then from the Mark Waypoint screen:
Enter a Name for the new waypoint (this is your site ID#; you might consider using
your initials and a #, ex. DW1)
-
Use Rocker & ENTR buttons to highlight
the name at the
top
of screen (by default a number 001, 002, etc)
-
Use Rocker & ENTR buttons to select
letters (to ‘type’)
-
When done entering letters, highlight OK on the
keyboard
& press ENTR
to close keyboard screen
Choose an Icon to represent the new waypoint on the map (Optional)
-
Use Rocker & ENTR buttons to select
the marker
symbol (by default a
flag, next to name)
-
Use Rocker & ENTR buttons to select
an icon
Average multiple positions for better accuracy (Critical for our
application!!!)
- Use Rocker & ENTR buttons to select AVG
- Wait… (counter
= # of positions to be averaged) (suggest you go for at least 20 positions)
- Use Rocker & ENTR buttons to select SAVE
-
Make sure you hit OK (see below) to Record Waypoint
Record Waypoint - (this is not Optional and
must be done in addition to any of the Optional steps above)
- Use Rocker & ENTR buttons to select OK at
the bottom of the Mark Waypoint screen
Data Downloading Back in the Lab: As with the previous data collection effort, it will be critical for you to overlay each of your points on our image to insure proper alignment and to move any points if needed. The following instructions (edited from those created by Stefan Freelan: J:\saldata\tut_GPS\Garmin_GPSmap60\4_GPSmap60_to_ArcMap_transfer.doc) will walk you through this process.
Transferring GPS Data from the
Garmin GPSmap60 to ArcMap
NOTE: These
instructions assume a certain degree of basic Windows operating system fluency
(coping files, creating folders, opening multiple applications, etc). If you do
not understand the instructions, please ask for help.
These instructions
are specific to the Spatial Analysis Lab (AH-16) computers and are customized
for local (Bellingham, WA) data and coordinate systems (UTM NAD27). Adaptations
will need to be made for other computers and/or other areas.
You will need a
Garmin GPSmap60-PC connection cable (hooks into the back of the GPS unit and
the PC), found on most SAL PC’s.
OPTIONAL: See also
J:\saldata\tut_GPS\Garmin_GPSmap60\Using_DNRGarmin.doc for an alternative method
of downloading data…
1. Connect the Cable
Connect the cable (from the back of
the computer) to the GPSmap60 (open the large rubber cover at top, right hand side of the
back of the unit and plug in the 4-prong connector). Note: the cable only fits
one way into the GPSmap60.
DO NOT FORCE IT – line up the small notch of the
plug with the guide.
2. Turn GPSmap60 ON (if it’s not already On)
- Press
and hold Power button on the top of the unit (next to antenna).
- If/when
prompted (because you are indoors), choose ‘Use with GPS off’
3. Open a Pre-made ArcMap project
file
- Open Windows Explorer or My Computer
- Browse to the J:\saldata\Esci442\lidar\arcgrids folder
- Double-click
on wwu.mxd
to open a pre-made ArcMap project (a simple map of the south WWU campus
that is in NAD83)
- If necessary,
right-click in the white space around (outside of) the map page and choose
Zoom Whole Page
4. In ArcMap Add the GPSi Toolbar
- Click on the View menu and
choose Toolbars
- Check the GPSi (not the GPS) toolbar option
5. Download Waypoints (or Tracks)
from the GPSmap60
- From the GPS Interface
toolbar, click the dropdown arrow and choose Waypoints (or Tracks)
and click on Download…
- In the Download… dialog
box choose the Waypoints (or Tracks) that you wish to download (there is
an All button on the right) and click on Save.
- In the Save… dialog box
browse to the C:\temp\ folder (or your desired location), enter a name for
your new GIS shapefile and click Save
- Repeat for Tracks and/or other Waypoints as desired…
- When done, turn the GPSmap60
OFF and remove the cable
6. View your data in ArcMap
Your GPS data should
be added automatically to the existing ArcMap project. NOTE: If your new shapefile does not show up in
your Table of Contents (the list of data layers on the left side of the
screen), click on the Source tab at the bottom of the Table of Contents,
then click on the Display tab to refresh the list. At this point, you points will not line up
well at all with your image. Each point
will probably be off by about 100m.
Don’t panic! This is because your
points come in from the Garmin unit using the WGS84 datum but our image is in
UTM NAD27. We need to reproject the
coordinates. This is a multistep
process.
6a.
Reproject from WGS84 to NAD83: In ArcToolbox, go
to Data Management Tools-Projections and Transformations-Feature-Project
Input
Dataset or Feature Class: shapefile with
your points
Input
Coordinate System: WGS84 (this is the default)
Output
Dataset or Feature Class: shapefile_NAD83
Output Coordinate System: click on
the 
to bring up the Spatial Reference Properties Dialog box- click Select.
Navigate to Projecied Coordinate
Systems-UTM-NAD83-NAD 83 UTM Zone 10N.prj
Click Add
Click Apply-OK
Geographic Transformation (optional): (not really optional!!!): Select NAD83 to WGS84
Click
OK. A Project Dialog box will open and inform you that the transformation
is complete but you will get a Datum conflict
between map and output warning message.
Ignore this.
6b. Reproject from NAD83 to NAD27: Again, In
ArcToolbox, go to Data Management Tools-Projections and
Transformations-Feature-Project
Input
Dataset or Feature Class: shapefile_NAD83
with your points
Input
Coordinate System: NAD1983_UTM_Zone_10N (this is the default)
Output
Dataset or Feature Class: shapefile_NAD27
Output Coordinate
System: click on the to bring up the Spatial Reference Properties Dialog box- click Select.
Navigate to Projecied Coordinate
Systems-UTM-NAD27-NAD 27 UTM Zone 10N.prj Click Add
Click Apply-OK
Geographic Transformation (optional): (not really optional!!!): Select NAD_1927_To_NAD1983_NADCON
Click OK. A Project Dialog box will open and inform you that the transformation
is complete
Your
points should now line up much better!
6c. Moving/Offsetting points: If one of your points does not line up perfectly or if you want to offset
one of your points (e.g. you logged a position adjacent to a building but you
want your point to be centered on the roof of the building), you can change
this. Go to the Editor dropdown and
select Start Editing 
. Then left click once on a point
to select it, then Left click, hold and drag the point to the correct
location. When you are finished editing
all points, go to Editor-Save Edits,
then Editor-Stop Editing.
6d. Adding coordinates to the
Attribute table: If you open the attribute
table for your points, you will note that it does not include the coordinates
for your points. To add this information
to the attribute table, go to the ArcToolbox and select WWU Tools-Add XY Coordinates.
Then simply specify your points file as the Input Feature and click
OK. Reopen your attribute table and the
coordinates should be there. At this
point, all you need to do is export the attribute table and save it as a .dbf
file. You can open this in Excel to
double check it and then e-mail it to me.
Other stuff you can
do in Arc:
Improve the Symbology for your GPS data
- Double-click on the name of your new waypoints (or tracks) shapefile
in the Table of Contents to open
the Layer Properties.
- Click on the Symbology
tab.
- Click the Import button.
- Click the drop-down arrow next to the Layer box and choose Point
(or TRACK, as appropriate)
- Click Ok. Click Ok again.
Explore
your data using ArcMap
- You can turn
your GPS data layers ON or OFF
(so they are visible or not) by checking the box next to the name in the Table
of Contents
- Use the Pan
tool (an open hand icon) to move left/right
- Zoom in/out using
the Zoom tools (the icon w/four
arrows pointing in for Zoom In, icon w/four arrows pointing out for
Zoom Out)
- You can use
the Measurement Tool
(the icon that looks like a ruler) to determine how far (in meters) your
GPS data varies from the photo
- Click on a waypoint or track using the Identify tool (the i
in a circle) to get the name, elevation, etc. of a waypoint or track
OPTIONAL: Print your map
- From the File
Menu, choose Print
OPTIONAL: Create and save a
.jpeg graphic of your map
- From the File
Menu, choose Export Map
- In the List
Files of Type box (lower left) scroll down and choose .jpeg
- Browse to your
U:\ drive, C:\temp\ or desired location to save your file
- Enter a name
in the File Name box
- Click OK
to export your map to a .jpeg graphic (this graphic could be inserted into
a PowerPoint slideshow, a Word document, a web page, etc.)
7.
OPTIONAL: Save your Map (to your U:\ drive)
- Save your .mxd (File / Save As) to your U:\ drive or desired location
- Close ArcMap (File / Close)
8. REQUESTED: Please Remove Files from the GPSmap60
Delete Waypoints: -
Press the FIND button and select Waypoints
- Press the MENU button
- Use Rocker & ENTR to select Delete
-
Choose All Symbols & press ENTR
-
Use Rocker to highlight Yes & press ENTR
Delete Active Track: - On
the Tracks screen, use the Rocker to highlight Clear
- Press ENTR
-
Use Rocker to highlight Yes & press ENTR
Delete Saved Tracks: -
On the Tracks screen, press the MENU button
- Use Rocker & ENTR to select Delete All Saved
-
Use Rocker to highlight Yes & press ENTR
***End of Stefan’s
instructions***
What if I can’t get my points downloaded from the Garmin? If you can’t get the download to work, there is another option, assuming that you have good field notes. In this case, simply use the coordinates that you wrote down in the field. Note that is will work ONLY if you set the unit to record and display coordinates in NAD83. Also, this is an instantaneous position so it will not be as accurate. You will need to check these coordinates in Arc. To do so, Go to Excel and enter your data in a format that looks like this:
|
SiteID |
Ycoord |
Xcoord |
|
|
DW1 |
5397690 |
537909 |
|
|
DW2 |
5397730 |
537857 |
NOTE THAT THERE ARE NO SPACES IN THE COLUMN HEADER NAMES AND NO SYMBOLS!!! Now go to File-Save As-Other Formats and save it as a “CVS (comma delimited)” file. This is a comma-delimited text file.
Then Open a Pre-made ArcMap project
file
- Open Windows Explorer or My Computer
- Browse to the J:\saldata\Esci442\lidar\arcgrids folder
- Double-click
on wwu.mxd
to open a pre-made ArcMap project
(a simple map of the south WWU campus)
In the Arc main toolbar, go to Tools-Add XY Data. In the Choose a table…. box, navigate to your .cvs file and then select the appropriate columns for the X and Y data values. Select OK and your points should plot on the image. Since you recorded these values directly from the Garmin in UTM NAD83, they should plot properly with no need to reproject. You may still need to Move or offset these points. If so, the easiest way to do this is simply to move your cursor to the correct location on the screen and note the UTM coordinates for this location at the very bottom of the Arc window. Then go back into Excel and enter these values into the correct column/row.
What To Turn In When: After you have checked all of your points, turn them in to me no later than Wednesday, 3/3 at 9:00AM. I need time to check all of your data prior to lab on Wednesday. You should email your data in an excel file that is a copy of: tree_data_entry_table.xls. Note that as soon as you enter the position of the plot center, I have set up formula that will calculate the position of each point.
If you have any problems or questions, don’t hesitate to ask for help.
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