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L 5. GIS Data Collection 1

Introduction to Geoinformatics

L-5. GIS Data Collection

Dr. Gyrgy SZAB associate professor

Budapest University of Technology and EconomyDepartment of Photogrammetry and Geoinformatics

[email protected]

ContentsOVERVIEWReviewing the main methods of GIS data capture and transfer and introduces keypractical management issues.LEARNING OBJECTIVES Primary (direct measurement) and secondary (derivation from other sources) data

capture for both raster and vector data types Describe data collection workflows; Understand the primary data capture techniques in photogrammetry, remote sensing

and surveying; Be familiar with the secondary data capture techniques of scanning, manual digitizing, vectorization,, and COGO feature construction; Understand the principles of data transfer, sources of digital geographic data, and

geographic data formats; Analyze practical issues associated with managing data capture projects.

Longley, Goodchild, Maguire, Rhind (2011): Geographical Information Systems and ScienceCH 9. pp. 229-249.

The six component parts of a GIS

Data

The Cost of Data Capturing(up to 85% of the total cost)

Stages in data collection projectsData Collection Workflow

Planning includes establishing user requirements, garnering resources, and developing a project plan.

Preparation involves obtaining data, redrafting poor-quality map sources, editing scanned map images, removing noise, setting up appropriate GIS hardware and software systems to accept data.

Digitizing and transfer are the stages where the majority of the effort will be expended.

Editing and improvement covers many techniques designed to validate data, as well as correct errors and improve quality.

Evaluation is the process of identifying project successes and failures.


Relation of GIS Extent and the Type of Data Capturing

100000

10000

1000

1000000

Techology

Scale

Regional Topography

[dm-m]

Global Geographyt

[10m-km]

Local Municipality

Utility [cm-dm]

Remote sensing Fotogrammetry

Surveying

Type and Importance of GIS data Collection

Importance/ cost/ technological complexities of GIS data collection

Primary data collection techniques: surveying, GPS, photogrammetry, remote sensing, inertial and mobile measuring systems

Advantage: good quality, precision, actuality Disadvantage: slow, expensive

Secondary data collection techniques: digitizing, scanning, transfer from existing data sources

Advantage: cheap, relatively fast Disadvantage: quality, actuality limitations

Raster Data Capture Remote sensing (Photogrammetry) is a technique used to derive information about the

physical, chemical, and biological properties of objects without direct physical contact Information is derived from measurements of the amount of electromagnetic radiation

reflected, emitted, or scattered from objects. Properties:

Resolution is a key physical characteristic of remote sensing systems. Spatial resolution refers to the size of object that can be resolved and the most usual measure is the pixel size. Spectral resolution refers to the parts of the electromagnetic spectrum that are measured. Temporal resolution, or repeat cycle, describes the frequency with which images are collected for the same area.

Aerial photography is equally important in medium- to large-scale projects Photographs are collected by analog optical cameras and later scanned, or by digital

cameras

Aerial Photographs are usually collected on an ad hoc basis Can provide stereo imagery for the extraction of digital elevation models Advantages are

- Consistency of the data- Availability of systematic global coverage- Regular repeat cycles

Disadvantages are Resolution is often too coarse Many sensors are restricted by cloud cover

Photogrammetry ...

Aerial Photogrammtery The sensors applied the visible part of the electromagnetic

spectrum and the central perspective geometry to form an image.

Photo interpretation: primary semantic interpretation of image content: interpretation of vegetation, artificial and other natural objects based on gray tone or color, texture, size, pattern, shadows

Photogrammetrical mapping: primary geometric interpretation of image content: digitizing the accurate positions of the object by correcting the perspective and height distortions.

Technology: Flight planning, 3D orientation of images, stereo compilation

Products: 3D vector maps, digital surface models (grid, contour line, profile), opthophoto

Typical photogrammetry workflow

(Reproduced by permission of GeoTec Media)


Methods and Products

x

z

y

1

3

2

4

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12

1

1

2

2

P

P

P

P

X

Z

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R

r . mo

r . mo

P

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Hpontosanmerleges felvtel

m mretarnyszmmal felnagytott ortofoto

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1. Tivadar aerial image

4. Tivadar Complex 3D model Orto rectification

vettsi centrum

X

Y

ZY

X

3 4

1 2

Y

X

3 4

1 2

Zeiss Photogrammetric CamarasLH Systems Digital Camera


Z/I Imaging Digital CamerasDMC, RMK-D Master Cone

4 RGB,NIR Color Cone

Panchromathic cone

Microsoft Vexcel UltraCam-XP

High Res PAN True Color

Color Infrared80% side overlap60% strip overlap

Remote Sensing ... Remotesensing Technology The active or passive sensors applied the wide part

of the electromagnetic spectrum (microwave, visible, infrared) and special geometry (point scanning, line scanning, panoramic images) to form an image.

Sensors, Imaging: SPOT, LANDSAT, IKONOS different geometric, radiometric, time resolution

Corrections: radiometric, geometric Automatic image interpretation: color

enhancement, Classification, Segmenting


(Source: John Jensen)

Spatial and temporal characteristics of commonly used Earth observation remote-sensing systems and their sensors Elektromagnetic spectrum

NASA Earth Observation Typical reflectance signatures for water, green vegetation, and dry soil

(Source: After Jones C. 1997. Geographic Information Systems and Computer Cartography. Reading, MA: Addison-Wesley Longman)

Budapest Landsat TM Image Landsat TM Supervised Classification


Derived Land Cover Map 2D, 3D Field Data Collection

SurveyingOrtogonal observations

Polar observations

Necessity of geodetical network

Time, money -> Cost

GPS applications Components: satellites in orbit, control network,

ground receiver Accuracy limitations: P Code, C/A Code,

Absolute, Differential, geometrical arrangement Applications: Geodetic accuracy survey control

point determination, Mobile navigation of cars, ships, airplanes

GPS GPS Theory

.

2 T

fc ==Based on electromagnetic propagation

Code observation (C/A, P code) - navigation

Phase observation (L1, L2) - surveying

Doppler slepp - movements

Time measurement:

9 nsec flutcuation/nap 10**-13 rel. Acc.

~ 2.7 m

Code distance

Phase distance

origin

Station


Observation types: absolute, relative

2-3

3-11-2

(x2,y2)(x1,y1)

(x3,y3)

(xA,yA)2-3

3-11-2

(x2,y2)(x1,y1)

(x3,y3)

(xA,yA)

Operational Systems

NAVSTAR USA global system 1978, full service 1995 Galileo EU test phase, operational 2013 Beidou China local test system COMPASS China global system GLONASS Russia global system IRNSS India regional system QZSS Japan regional system

Mobile Maping Systems

Producing near real-time 3D digital terrain model Components: Navigation part: GPS, IMU, Imaging

part: digital camera, laser scanner, video, RS sensor, Integration unit: component control , and data storage

Platforms: Ship for hydrology data collection, Car for road data collection, Airplane for complex regional terrain modeling, Satellite for global monitoring

Vide

Lidar System Theory(Light Detection and Ranging)

GPS + IMS

X,Y,Z Fi,Om,KaLidar Scanner

V=50-200 m/s

Szkesfehrvr:Lidar and Photogrammetry Integration

Lidar point cloud (2x 45 M point, 5-10 point/m2), Ortophoto (20Mpixel, 0,5m RGB, NIR), Surveying base map (3Mbyte), Terrestrial lidar (25M pont/ha 2500 point/m2)


Digitizing Maps

Preparation-highlight the theme, Digitizing - transformation, manual processing, Data editing error correction, forming topology, Advantage - inexpensive equipment, little training, poor

map quality, Disadvantage - tedious, time consuming

Scanning Preparation-cartographic quality, clean, Scanning geometric, radiometric calibration, resolution, accuracy, Data editing thinning and vectorization, separation to line, symbol and noise ,

error correction, coding, forming topology, Integrating image data in GIS scanned maps, documents, photographs,

satellite data, video images , Advantage easily performed, rapid compilation, Disadvantage - manipulation of large raster files, missing attribute linking, poor

intelligence, required good map quality, complex equipment, expertise required

Adjacent raster cells with the same attribute values are aggregated. Class boundaries are then created at the intersection between

Batch vectorization of a scanned map

(A) original raster file

(B) vectorized polygonsB

A

(A) undershoots and overshoots

Examples of human errors in digitizing

(B) invalid polygons

(C) sliver polygons

Error induced by data cleaning. If the tolerance level is set large enough to correct the errors at A and B, the loop at C will also (incorrectly) be closed.

Mismatches of adjacent spatial data sources that require rubber sheeting


GIS Data from External Sources One of the biggest problems with data obtained from external sources is that they can be

encoded in many different formats. Many tools have been developed to move data between systems and to reuse data

through open application programming interfaces (APIs). More than 25 organizations are involved in the standardization of various aspects of

geographic data and geoprocessing ISO (International Standards Organization) is responsible for coordinating efforts

through the work of technical committees TC 211 and 287 In Europe, CEN (Comit Europen de Normalisation) is engaged in geographic standardization. OGC (Open Geospatial Consortium) is a group of vendors, academics, and users

interested in the interoperability of geographic systems Geographic data translation software must address both syntactic and semantic translation issues. Syntactic translation involves converting specific digital symbols (letters and numbers)

between systems. Semantic translation is concerned with converting the meaning inherent in geographic

information.

Comparison of data access by translation and direct read

NSDI National Spatial Data Infrastructure German Land Management System

Topographic systems conceptATKIS

Feature CatalogueRules of depiction of topographic

information in the DLM

Symbol CatalogueRules for cartographic representation

of the information in the DKM

GermanBasicMap 1:5000

D DigitalL LandscapeM Models

D DigitalT TopographicK Map

Mapcapturingmodelling

cartographicprocess

preparationfor output

User of digital data

UniformDataBase

Interface

EDBS

TIFF

Evaluation of Topographic IS > EU INSPIRE


Infrastructure for Spatial Information in Europe

DIRECTIVESDIRECTIVE 2007/2/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCILof 14 March 2007establishing an Infrastructure for Spatial Information in the European Community (INSPIRE)

Relationship between quality, speed, and price in data collection

Quality

Price

Thank You

MerciGrazie

Gracias

Obrigado Danke

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