Basic Geodetics What Every GIS User Should Know

Transcription

1 Experts in Geomatics, Surveying, Positioning, Geospatial Data, and Mapping Sciences Basic Geodetics What Every GIS User Should Know Michael Barnes Cain & Barnes LP Steven Long Shell May 9, 2013

2 Knowledge Data Zone of the Geodetic Quagmire Techniques Tools Source: Cain & Barnes LP 2

3 Knowledge Basic Geography College, University Industry Training Learning & Development Data Basic Geodetics Techniques Tools 3

4 The least you need to know for Geospatial Data Management Geodetic Awareness of 5 Facts: 1. Geodetic Datum 2. Map Projection 3. Vertical Reference 4. Reference Orientation 5. Unit of Measurement 4

5 Geodetic Reference Surfaces h H N Normal to Ellipsoid Normal to Geoid N=h-H Ellipsoid Geoid Terrain b a Geoid Equipotential surface which approximates to MSL Ellipsoid Surface where Computations are made 1/f = a/(a-b) Source: APSG 5

6 Examples of Geodetic Datums 6

7 How many geodetic datums? Review 7

8 Before GPS we had 150 years of geodetic surveying e.g. National Geodetic Survey of Nepal

9 Hierarchy of Mapping Ellipsoid λp Equator Yp Φp hp P Zp Xp Projected CRS is a derivative of the Datum (Geog CRS) Easting, Northing, Elevation (above MSL) stable Unstable w/o Datum Datum (ellipsoid & origin) is the Foundation X,Y,Z Cartesian and Lat, Long, Ht Source: APSG 9

10 What are the main map projections in use? Mercator Transverse Mercator Universal Transverse Mercator Lambert Conformal Conic Others less frequently: Stereographic, Oblique Stereographic, Oblique Mercator, et. al. 10

11 Vertical Reference: Height, elevation, vertical datum or what? Local Kelly-Bushing, ground level, sea level, and assorted other local references Geodetic Either directly or derived from Mean Sea Level at one or more points at some epoch examples: NGVD 29, NAVD 88, IGLD85, OSU91A, EGM96, EGM2008 Tidal Defined by direct observation of tidal variations over some period of time at a specific location (or locations) examples: MSL, LAT, MLLW, MLW, MHW, MHHW 11

12 Potential for confusion with Local Vertical Datum Source: UKOAA, now OGP 12

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14 Reference Orientations (5 kinds of north) True North = Direction of the meridian through a point Magnetic North = Differs from True North by declination and varies with time Grid North = Differs from True North by convergence Gyro North = a measurement of True North by instrument Plant North = strictly a local non-georeferenced orientation 14

15 Units of Measurement (13 kinds of feet and 2 kinds of meters in use) Reference Units: Biggest E&P Problem US Survey Foot vs. International Foot 1 ftus = ft (Intl), but this is still important for UTM, generating foot errors, depending on latitude Other Feet: Clarke s Foot, Sears 1922, 2 for Benoit (both 1895), Gold Coast Ft., 4 Indian Ft. (1865, 1937, 1962 & 1975) and 2 British Feet (1865 & 1935), 2 meters: International Meter and German Legal Meter Other linear units include Chains, Links, and Yards 15

16 If you remember nothing else.. Latitudes and Longitudes are not unique unless qualified with datum name Projection Coordinates are not unique unless qualified with Projection name, Zone and Datum Heights are not unique unless qualified with Surface Reference (Vertical Datum) Orientations are not unique unless qualified with Heading Reference Units are not unique unless qualified with Unit Reference 16

17 Knowledge Basic Geography College, University Industry Training Learning & Development Data Acquisition & Sourcing Processing & Integration Integrity & Handling Data basing & Retrieval Basic Geodetics Techniques Tools 17

18 Corporate Geospatial Data Managed at global or business unit level Company Propriety data Lease boundaries and licensed areas Seismic Well data Topographic and bathymetry Site survey and environmental data Infrastructure (pipelines, platforms, cables..) Third party industry data Seismic Well database Geologic data High resolution satellite imagery Gravity and magnetics 18

19 Past, Present, and Future Geodetic Integrity of Geospatial Data requires Source: OGP GIGS 19

20 Fundamental Exploration Data Sets Seismic surveys Wells, surface and well bore locations Boundaries, lease and license areas 20

21 Source: OGP 21

22 Source: OGP 22

23 80% + of all GG&E data Easting and Northing, X and Y or Y and X? Units of Measure stated? e.g. US Survey Foot International Foot Meter, etc Mandatory Metadata 23

24 NAD83 Seismic Survey incorrectly mapped as NAD feet of error as a block shift 24

25 Commercial Well Location Data Source: APSG 25

26 Digital Land Grids (Cadastral) Source: APSG 26

27 Area Discrepancy due to Incorrect Grid 27

28 Example Unit with Discrepancies Measured 28

29 Various State & Vendor Database Well Locations 29

30 Source: Conner 30

31 Source: Conner 31

32 Reasons for Mislocation of Wells Accuracy and reliability of original measurement systems and cartographic layers Miscalculations and poor QC Error in transformation of Coordinate Reference Systems Transcription errors, data entered incorrectly Transposing legacy data via new technologies Inadequate documentation Lack of industry standards for surveying and mapping 32

33 Well Surface Locations are frequently wrong Source: EnSoCo 33

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35 Innovations in data use still requires sound geodetic and mapping principles 35

36 This image cannot currently be displayed. Time Lapse Plant refurbishment Iraq 7 months of overlay data 36

37 Geo-Information Integration 2010 DEM 2006 photography 1964 Surficial Geology 1968 topo 2012 topo 2012 aerial 37

38 Seismic Project, Wyoming Twenty Four 2D Data Geodetic Parameters Options NAD27 NAD83 WGS84 NAD27 / BLM 12N (ftus) NAD27 / BLM 13N (ftus) NAD27 / UTM zone 12N NAD27 / UTM zone 13N NAD27 / Wyoming West NAD83 / BLM 12N (ftus) NAD83 / BLM 13N (ftus) NAD83 / UTM zone 12N NAD83 / UTM zone 13N NAD83 / Wyoming West NAD83 / Wyoming West (ftus) NAD83(HARN) / UTM zone 12N NAD83(HARN) / UTM zone 13N NAD83(HARN) / Wyoming West NAD83(HARN) / Wyoming West (ftus) NAD83(NSRS2007) / UTM zone 12N NAD83(NSRS2007) / UTM zone 13N NAD83(NSRS2007) / Wyoming West NAD83(NSRS2007) / Wyoming West (ftus) SPCS83 Wyoming West zone (meters) SPCS83 Wyoming West zone (US Survey feet) 38

39 CRS Metadata inadequate? What is mislocation risk? NAD27 NAD83 WGS84 NAD27 / BLM 12N (ftus) NAD27 / BLM 13N (ftus) NAD27 / UTM zone 12N NAD27 / UTM zone 13N NAD27 / Wyoming West NAD83 / BLM 12N (ftus) NAD83 / BLM 13N (ftus) NAD83 / UTM zone 12N NAD83 / UTM zone 13N NAD83 / Wyoming West NAD83 / Wyoming West (ftus) NAD83(HARN) / UTM zone 12N NAD83(HARN) / UTM zone 13N NAD83(HARN) / Wyoming West NAD83(HARN) / Wyoming West (ftus) NAD83(NSRS2007) / UTM zone 12N NAD83(NSRS2007) / UTM zone 13N NAD83(NSRS2007) / Wyoming West NAD83(NSRS2007) / Wyoming West (ftus) SPCS83 Wyoming West zone (meters) SPCS83 Wyoming West zone (US Survey feet) 39

40 Same X,Y numbers used with different map projections NAD27 / Wyoming West or NAD83 / Wyoming West (ftus) Project Working West Wyoming Data on Vacation Nebraska State Park 40

41 Geo-Information Integration? Project GIS had 168 spatial layer 41

42 3D printing direct from GIS data 42

43 OGP ESPG Area Polygons reducing risk in handling of geodetic data 2,900+ polygons available online Source: OGP 43

44 Example: Nigeria Onshore and EEZ Rectangular Bounding Box 11 geodetic datums 13 Projected CRS* 25 transformations Geographic Area Polygon 3 geodetic datums 9 Projected CRS* 13 transformations * = datum + map projection 44

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46 Knowledge Basic Geography College, University Industry Training Learning & Development Data Acquisition & Sourcing Processing & Integration Integrity & Handling Data basing & Retrieval Basic Geodetics Techniques Tools GNSS (GPS) Positioning GIS Mapping Geoscience Software Engineering Software Source: Cain & Barnes LP 46

47 Source: Schostak 47

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53 Geospatial Integrity Compliance Grade????

54 Data Acquisition & Sourcing Processing & Integration Integrity & Handling Data basing & Retrieval Basic Geodetics Techniques Standards & Practices Procedures & Workflows Quality Control Processes Continuous Improvement Tools GNSS (GPS) Positioning GIS Mapping Geoscience Software Engineering Software 54

55 Forensic Geodetics of Well Location (US GOM) Followed the data from G&G through Drilling Operations 486 documents with well location stated Location stated as X and Y Often stated as UTM 16N ftus (aka BLM) NAD 27 and NAD 83 both are relevant 40% had no datum stated Geoscience data handling in UTM 15 and 16 at various stages of process Positioning difference is. Cost of the well is 55

56 NAD27 / UTM 15N vs. NAD83 / UTM 15N Positioning difference is 656 feet Cost of Well US$ 85 million 56

57 Transforming Coordinate Reference Systems Concatenated data operations are not trivial Source: OGP EPSG Registry 57

58 Knowledge Basic Geography College, University Industry Training Learning & Development Data Basic Geodetics Techniques Tools 58

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60 Demographics of Participants

61 Relevant and Useful?

62 Data Tools Zone of the Geodetics Quagmire Knowledge Techniques 62

63 Agenda Defining a GIS Project Working in ArcMap Dissemination of Geo-Information Summary

64 Overview GIS Project Setup What is my area of interest? How do I determine valid coordinate reference systems for my area of interest? What is the preferred coordinate reference system? Working in ArcMap What happens when I import my data into ArcMap? What is the preferred transformation? What is the maximum error if incorrect transformation is selected? Dissemination of Geo- Information Web Maps 3D Viewers Map Products Potential for geodetic integrity issues at all stages

65 Agenda Defining a GIS Project Working in ArcMap Dissemination of Geo-Information Summary

66 GIS Project Lifecycle Mandatory Coordinate Reference System (CRS) definition at project framing phase Coordinate Reference Systems (CRS) Ensure CRS validation for all subsurface applications Geomatics experts contacted at project start-up Source: McLay (2007) Users should not make assumptions regarding CRS!

67 Determining Coordinate Reference System OGP EPSG Area Polygons Reduces risk in handling of geodetic data polygons available online Source: OGP

68 OGP EPSG Area Polygons Download shapefile and load directly into ArcMap Area of Interest

69 EPSG Geodetic Parameter Registry Structured dataset of Coordinate Reference Systems and Coordinate Transformations Options to query by filter or retrieve by code Source: OGP

70 EPSG Geodetic Parameter Registry (con t) Source: OGP

71 Recommendations for CRS Selection Select an appropriate 2D geographic CRS ( datum ) which is in common use and has an accepted and well defined transformation to WGS 84 Use an appropriate map projection that is in common use and has small distortions Consider existing legacy data Consider export of produced data / maps (i.e., regulatory reporting requirements) Objective is to minimize geodetic risk Obvious choice is not always the best

72 Agenda Defining a GIS Project Working in ArcMap Dissemination of Geo-Information Summary

73 Geodetic Integrity and ArcGIS ArcMap has the ability to transform and re-project on the fly Can display data stored in one CRS as if it were in another, without altering the actual data Data frame s CRS is defined by the first layer added to the data frame or by manually setting the CRS through the data frame properties But there is no help to the user for the selection of the preferred transformation

74 Transformations When To Use A transformation is required when changing coordinates from one CRS to another CRS (i.e., NAD27 to WGS 84) Transform? No Transformation Required Source CRS: NAD27 Target CRS: NAD27 Transform? Transformation Required Source CRS: NAD27 Target CRS: WGS 84

75 Out-of-the-box ArcGIS Transformation No information about what are the differences between these transformations Which one is the preferred transformation?

76 Custom Transformations Users have the ability to create custom transformations Consult your local geodetic expert!

77 North American Preferred Transformations Transformations from NAD27 to NAD83 (WGS 84) NADCON - Alaska NTv2 NADCON - Conus

78 Difference Between NAD27 and NAD83 Source: Wikipedia

79 Agenda Defining a GIS Project Working in ArcMap Dissemination of Geo-Information Summary

80 Web Maps Increasingly popular medium for displaying spatial information Uses internet browser Questions: 1) Do you know what coordinate reference system is being used by the application? 2) Do you know the coordinate reference system of your input dataset? 3) Do you know what transformation is being used between the application and the input datum? Source: ESRI Beware of your input data properties and data operations performed by application

81 3D Viewers ArcGIS Explorer and Google Earth Both allow input and display of GIS data How is this data handled? ArcGIS Explorer (Build 1750) Google Earth Pro (version ) Better integration with GIS data Uses WGS 84 as CRS Should only be used for small / medium scale mapping NADCON not supported Can consume shapefiles Uses WGS 84 as CRS Fitting of images of different types causes some of the images to be distorted. How much? Not advisable to do large scale digitization from images Need to transform input datum into WGS 84

82 Map Products All maps should have the coordinate reference system as the minimum; Name and EPSG code EPSG code is standard for oil and gas industry Example EPSG Name: NAD27 / BLM 15N (ftus) EPSG Code: ESRI names are not EPSG compliant Look up codes in EPSG Geodetic Parameter Registry

83 Summary Don t make assumptions regarding coordinate reference systems Don t assume the software sorts out your geodetic problems Make use of OGP EPSG polygons and EPSG geodetic parameter registry Seek advice from geodetic experts when in doubt

84 More than 460 experts in Geomatics, Geodetics, Surveying, Positioning and Navigation, Geospatial Data, and Mapping Sciences Apply online to join for professional development, technical education, business networking, and fellowship