1. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
UNSD Workshop
Pieter van Jaarsveld
Mobile GIS Specialist
An Overview to a professional GPS/Mapping collection solution
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

2. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Survey
Recreational GPS users?
In-car navigation users?
Capturing GPS data in the field for GIS use?
Plan to in the next year?
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

3. Global Positioning System
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

4. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
What is GPS?
Global Positioning System
Where on earth am I ?
Constellation of satellites
Handheld devices
Various Applications
Accuracy
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

5. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
GPS in 5 Basic Steps 1
Correct for Atmosphere & Ionosphere
Differential
Corrections 4 3
Trilateration using speed of light
Accurate clocks
are required 2
Use ephemeris for satellites’ location 5
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

6. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007

7. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Control Segment
Provides worldwide coverage and control
365/24/7
Master Control station
Colorado
Four support stations
Hawaii
Kwajalein
Diego Garcia
Ascension Island
OK so lets take a slightly more detailed look at the control segment.
It provides worldwide coverage and control 24/7 356 days of the year. This continual monitoring is critical to ensuring each satellite is positions correctly and its health is monitored and reported to the user segment.
There is a master control station in Colorado and four support stations distributed through out the major oceans maintaining contact with each satellite for each quadrant of the earth.
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

8. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Space Segment
GPS satellite constellation
24 satellites
Replenishment occurring
Satellite design
Lifetime 7.3 years
16 satellites over
9 years old
The space segment itself consists of 24 operation satellites. At all times there are at least three satellites in reserve.
The reserve satellites are used to replace any operation satellite that becomes un-healthy.
Replenishment of the satellites is continually occurring to maintain the constellation and ensure accurate positioning is visible in the future.
Current lifetime of the satellites in orbit is 7.3 years, far beyond their expected lifetimes. There are 16 over 9 nine years old.
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

9. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
User Segment
Equipment produced by Military and Private companies
Receives signal and computes
Position
Time
Velocity
The user segment consists of both military and private users. It is important to note there are two separate signals, one for military operations and another for commercial sector. I’m only going to focus on the commercial sector today…
The uses of GPS in the user segment are very diverse and basically touch on all aspects of our life from handling financial transactions through to landing the planes and of course managing our geographic information!!!
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

10. How do we position ourselves?
Simple Geometry
Velocity times vs travel time
Determine Radio Wave Time Travel
Accurate timing
Measure Distances
Known orbit locations
Trilateration
Distances not angles
The basis of GPS is "triangulation" from satellites.
To "triangulate," a GPS receiver measures distance using the travel time of radio signals.
To measure travel time, GPS needs very accurate timing which it achieves with some tricks.
Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret.
Finally you must correct for any delays the signal experiences as it travels through the atmosphere.
In a sense, the whole thing boils down to those "velocity times travel time" math problems we did in high school. Remember the old: "If a car goes 60 miles per hour for two hours, how far does it travel?"
Velocity (60 mph) x Time (2 hours) = Distance (120 miles)
In the case of GPS we're measuring a radio signal so the velocity is going to be the speed of light or roughly 186,000 miles per second.
The problem is measuring the travel time.
The timing problem is tricky. First, the times are going to be awfully short. If a satellite were right overhead the travel time would be something like 0.06 seconds. So we're going to need some really precise clocks. We'll talk about those soon.
But assuming we have precise clocks, how do we measure travel time? To explain it let's use a goofy analogy:
Suppose there was a way to get both the satellite and the receiver to start playing "The Star Spangled Banner" at precisely 12 noon. If sound could reach us from space (which, of course, is ridiculous) then standing at the receiver we'd hear two versions of the Star Spangled Banner, one from our receiver and one from the satellite.
These two versions would be out of sync. The version coming from the satellite would be a little delayed because it had to travel more than 11,000 miles.
If we wanted to see just how delayed the satellite's version was, we could start delaying the receiver's version until they fell into perfect sync.
The amount we have to shift back the receiver's version is equal to the travel time of the satellite's version. So we just multiply that time times the speed of light and BINGO! we've got our distance to the satellite.
That's basically how GPS works.
Only instead of the Star Spangled Banner the satellites and receivers use something called a "Pseudo Random Code" - which is probably easier to pronounce and sing than the Star Spangled Banner.
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

11. Sources of Positioning Error
Ionosphere and Atmospheric delays
Satelite and receiver Clock Error
Multipathing
Dilution of Precision
Receiver Issues
Selective Availability
Like any system there are always errors to account for…so what are the core error sources in GPS.
Errors can be grouped into the six classes:
1)   Multipath--Errors caused by reflected signals entering the receiver antenna
2)   Ionosphere--Errors in the corrections of pseudorange caused by ionospheric effects 3)   Ephemeris data--Errors in the transmitted location of the satellite 4)   Satellite clock--Errors in the transmitted clock
5)   Receiver issues – which really boil down to hardware and positioning engine implementations
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

12. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Differential GPS
Two receivers track the SAME signals and errors at the SAME time
Derived corrections are then applied to the data during postprocessing
GPS Analyst contains tools for DC
Does not correct multipath
Data Collector
Base
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

13. Differential Correction
Red = Uncorrected GPS
Green = GPS after differential correction
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

14. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Selecting a GPS
Recreational versus Professional GPS
Accuracy
Tens of meters versus sub meter
GIS data integration
Format conversion
Attribute collection
Customised forms, business rules
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

15. Data Collection Software
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

16. Data Collection Workflow (server to server)
Desktop
Mobile
Desktop
Server
Export to PGDB
Check out
Copy to device
Copy to Desktop
Check In
Post process
Import to Enterprise
Data validation
Enterprise Geodatabase
ArcPad
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

17. Data - things to remember
Check out and post processing is performed on a personal geodatabase NOT directly from enterprise. WHY?
GPS detail not required in enterprise
Topology not supported in GPS Analyst
Carefully choose extents. WHY?
Large extent limits the amount of data capture
Current only personal geodatabase support, efforts to supporting file geodatabase underway.
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007
UC 2007 Tech Sessions 17 17

18. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
What is ArcPad?
Part of ESRI overall mobile strategy
A mobile GIS application for field mapping applications
Designed for broad range of mobile systems
Allows input from GPS receivers, rangefinders, digital cameras and other devices
Provides a generic set of mobile GIS functionality
Extensive customization capabilities
Extends Geodatabase to the field through disconnected editing
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

19. What can you do with ArcPad?
Use your existing data
Add data from the Internet
Move around your map
Query your data
Edit your data
Measure distance, area, and bearings on your map
Navigate with your GPS
Customize ArcPad to streamline your workflow
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

20. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
ArcPad Benefits
Streamlines the workflow
Smart, task oriented solutions
Increases productivity
Reduces office work and data entry time
Improves the accuracy of data
Resulting in more accurate and current data for analysis and decision making
Traditionally, paper maps are what used in the field by mobile workers. Field edits were performed using sketches and notes on these paper map. Once back in the office, these field edits were then manually entered into the GIS database.
The ArcPad workflow as outlined before has enormous productivity gains - it eliminates the major portion of office work previously required to integrate the field data with the enterprise GIS database. But, more importantly, it significantly improves the accuracy of the field GIS data, and consequently improves the accuracy, currency, and integrity of the enterprise GIS database - resulting in more accurate and current data for analysis and decision making. This is a major benefit of mobile GIS applications.
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

21. ArcPad Functionalities
Improved performance
Enhanced editing tools
Snapping
Undo
offsets for points, lines, polygons
repeated features
segmented line features
Camera and rangefinder support
Improved symbology and labeling
Support for Graphics layer
for redlining or mark-up
Import/export tools for ArcGIS
Customization
wizard for creating custom forms
ArcPad 7 offers enhancements in the areas of performance, ease of use, productivity, enterprise GIS integration and customization.
New features include
Quicker access and loading of spatial data
Advanced editing tools, including offsets, repeated attributes, segmented line features, snapping, and undo
Support for ArcGIS symbology and style sheets - Maps look the same in ArcMap and ArcPad and more labeling options
Integrated support for rangefinders and digital cameras
Support for freehand marking and taking notes on maps
ArcPad 7 includes additional tools for ArcMap which are automatically
installed with ArcPad. These new tools allow you to:
• Extract data for use with ArcPad 7 and/or check data out of a
geodatabase for editing.
• Export symbology for selected shapefiles into ArcPad Layer files.
• Export/import an ArcGIS Graphics Layer to/from an ArcPad Graphics
layer.
• Export ArcGIS styles to an ArcPad style.
Simple form customization within ArcPad
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

22. ArcPad Functionalities
Significant performance gains on startup time
Pre-buffering input
Affects Applets, Layers, Scripts etc. (i.e ALL XML and Scripts)
Delayed loading of projection data
Usability enhancement
Datum conversion wizard
Picture browsing capabilities on Windows Mobile 5 devices
Additional language packs available
Quality improvements
About 80 bugs have been identified and fixed!
Minor feature improvements
Object model improvements (Picture chooser, File object , Inter-process methods)
ArcPad 7 offers enhancements in the areas of performance, ease of use, productivity, enterprise GIS integration and customization.
New features include
Quicker access and loading of spatial data
Advanced editing tools, including offsets, repeated attributes, segmented line features, snapping, and undo
Support for ArcGIS symbology and style sheets - Maps look the same in ArcMap and ArcPad and more labeling options
Integrated support for rangefinders and digital cameras
Support for freehand marking and taking notes on maps
ArcPad 7 includes additional tools for ArcMap which are automatically
installed with ArcPad. These new tools allow you to:
• Extract data for use with ArcPad 7 and/or check data out of a
geodatabase for editing.
• Export symbology for selected shapefiles into ArcPad Layer files.
• Export/import an ArcGIS Graphics Layer to/from an ArcPad Graphics
layer.
• Export ArcGIS styles to an ArcPad style.
Simple form customization within ArcPad
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

23. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Configuring the GPS
Protocol = “Trimble GPSCorrect” or “NMEA0183”
Port = “COM3: TSIP Serial Port (GeoExplorer)
Port = “COM7: TSIP Serial Port (JunoST)
Port = “COM2: TSIP Serial Port (Recon XC)
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

24. Streaming and Averaging
number of incoming GPS position coordinates that ArcPad uses for calculating an average coordinate
Streaming
Position Interval = How frequently ArcPad uses incoming GPS coordinates
Distance Interval = ArcPad uses incoming GPS coordinates only when greater than this distance from LAST coordinate used
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

25. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
GPS Preferences
Quality
Minimum and maximum values can be predefined
Can be made compulsory to ensure data integrity
Warning and Alerts
Visual and Audio alerts
Constantly warns the user if not complying to presets
Will inform the user of GPS status
Can be annoying
Can be switched off
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

26. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Editing using the GPS
Firstly, make layer editable (one point, line, polygon, at a time)
Then select feature type
Then select GPS capture tool
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

27. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Ensuring data quality
Elevation Mask
Default 15
No. of Satellites
Min of 4 SV’s
SNR
Signal to
Noise Ratio
High = Accurate
Low = Productive
DOP
SV Geometry
High = BAD
Low = GOOD
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007
UC 2007 Tech Sessions 27

28. ArcPad with other devices
ArcPad can be used with:
Digital Cameras
WiFi enabled cameras
BT enabled camerasUse “Camera” tool
Photo Layer
Custom Form
Laser Rangefinders
What is your accuracy needs?
External GPS
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

29. Data Collection Techniques
Where are the Satellites?
Your Body is an obstruction!
Point Data Collection
Position First and Attributes Second
Polyline & Polygon Collection
Streaming (less accurate but dynamic)
Vertex Averaging (more accurate and static)
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007
UC 2007 Tech Sessions 29

30. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
ArcPad Tips and Tricks
Do you understand Sticky Keys?
Have you used appropriate colours and line thicknesses?
Is your device locked?
Don’t you pick on me! (Avoid clicking on the map)
The art of using a stylus
Slow down and smell the flowers! 
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007
UC 2007 Tech Sessions 30

31. ArcPad Orientation Demonstration
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007

32. UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12 October 2007
Thank you
Mobile GIS Specialist
(011)
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia October 2007