GIS Data Collection

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GIS Data Collection

• Christopher R. Bennett
• EASTR

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Overview of Presentation

• Introduction
• Spatial Data
• Options for Collecting GPS Data
• Examples of Output

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Introduction
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Background to Project

• Sponsored by EAP Innovation Fund
• 30k to investigate spatial tools for project
  preparation and supervision
• Project looked at
• Opportunities for spatial data on projects
• Data collection techniques
• Ways of managing data

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Findings

• Project completed January 2006
• Recommended EAP commit to using spatial data on
  projects
• Proposed
• Using GPS Enabled Camera to collect data
• Google Earth to manage data

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Spatial Data
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Spatial Referencing

• Any location can be expressed as the latitude and
  longitude
• A unique and permanent way of identifying location

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Types of Data

• Vector
• Points, lines (two or more points) and polygons
  (multiple lines)
• Each point is represented by (x,y) co-ordinates
  corresponding to latitude and longitude
• Raster
• Usually images

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Ways of Collecting Data

• GPS Surveys
• Data collected using Global Positioning System
  (GPS)
• GPS uses satellites and triangulation to get the
  location
• Digitizing
• Existing maps are converted to digital
• Aerial Photos and Satellites

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Principles of GPS Measurement

• Run by US Department of Defense
• 24 satellites at 20,200 km altitude
• Normally 5 satellites can be viewed anywhere in
  the earth
• Satellite sends a radio timing signal
• Time measurements used to establish distance from
  satellite

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GPS Locations

• By observing a minimum of 4 satellites (3
  position 1 for time) location can be established
• More satellites in view gives better accuracy

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GPS Accuracy

• Depends on
• The number of satellites in view
• The equipment
• Typical consumer equipment /- 8 10m with 95
  confidence
• Survey grade instruments /- 2 m or better
• Accuracy improved by
• Differential correction
• Signal from GPS base station or similar

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Example of GPS Accuracy
Uncorrected /- 1.2 6.3 m Corrected /- 1.1
1.6 m
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Example of GPS Accuracy - Apia
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Options for Collecting GPS Data
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Overview

• Project field tested different equipment
• Handheld GPS receiver
• Personal digital assistant
• GPS enabled camera
• All were found to be suitable for us

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Data Needs

• GPS data
• Point data data at a single location (x,y)
• Continuous data set of (x,y) data representing a
  line (eg road)
• Most preparation and supervision projects need
  point data
• Spatially referenced digital photographs valuable

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Data Definitions

• Important to ensure consistency when defining
  what data collected
• Identified simple codes for range of issues

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Handheld GPS Receivers

• Many different types available
• Consumer models cost
• Project use Garmin e-Trex
• Garmin most widely supported by 3rd party
  software
• Can store about 10,000 points
• 12 channels so should give good accuracy

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Garmin Findings

• Robust unit with good battery life (17 h for 2 x
  AA batteries)
• Very simple to use in the field
• For continuous data travel to site and turn on
• Useful to have windscreen mount for unit
• Not easy to enter point data description

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Personal Digital Assistants (PDAs)

• Tested Windows based PDA with CF-Card GPS
• Data Collected with
• Custom software
• Data Logging
• GPS2Googe Earth

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PDA - Pocket PC Creations

• Software designed for rapid development
• Data ported to access
• Good for proof-of-concept
• Several problems
• Was not able to collect continuous data
• Difficult to install
• Expensive to deploy

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PDA - GPS Data Logging

• Many applications store GPS data
• Simple to use
• Turn on GPS
• Software logs data
• Only disadvantage was inability to store point
  data

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PDA - GPS2Google Earth

• Low cost (
• Simple application to record point and continuous
  data and export GE files
• Simple to use and with some refinements ideal for
  Bank data collection

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Digital Photographs and GPS

• Digital photos (.JPG files) can have spatial
  co-ordinates added to header
• When read into GIS/GE image correctly postioned.
• Two options
• Link digital photos to GPS log data
• GPS enabled camera

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Digital Photos Linking To GPS

• Time of photo matched to GPS log data
• Used Robogeo (v 3) (50) software
• After GPS data matched created GE file

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Robogeo Matching
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Digital Photos GPS Camera

• Camera with embedded GPS records spatial data
  along with photo
• Very easy to use
• Project tested Ricoh Pro-G3
• More details in next presentation

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Examples of Outputs
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Comparison of 3 Devices

• Recorded data in same location with Handheld GPS,
  PDA and GPS Camera
• Excellent agreement

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Shiman Highway Project 1
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Shiman Highway Project - 2
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Shiman Highway Project - 3
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Cambodia GIS Import
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Thailand GPS Image
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Satellite Image
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For More Details

• Download the report Using Google Earth on World
  Bank Projects from www.lpcb.org

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The End