DOCSLIB.ORG

FME Coordinate Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
FME Coordinate Systems Coordinate Systems All FME features know about their coordinate system and, therefore, their location on the earth. An FME coordinate system contains a complete mathematical model of the conversion between a specific location on the earth and a set of coordinates. Coordinate system definitions are spec- ified by a set of parameters that define this mathematical model, including the earth model (ellipsoid or datum), the units used to measure the coordinates, the projection type, and any parameters specific to the projection type. Coordinate systems may be extracted from input feature data sources, may come predefined with the FME, or may be defined by FME users. The FME allows output coordinate systems that are different than the input ones to be specified and performs the required coordinate con- versions when necessary. FME is shipped with over 5000 coordinate systems based on a variety of different projections, ellipsoids, and datums. The file coordsys.db in the FME installation directory contains the names and descriptions of all predefined coordinate systems. However, some users may wish to use coordinate systems that do not ship with FME, and will need to read the topics on defining custom coordinate systems. When an FME reader knows its coordinate system, the FME creates a coordinate system to match the input data specification and tags each fea- ture read with this system name. However, a majority of formats do not explicitly store the coordinate system. In such cases, mapping file direc- tives are used to supply coordinate system information. The mapping file may also contain a specification as to which coordinate system the output data is to be in. If the output coordinate system is specified and it is different from the input coordinate system, then the FME automatically converts the feature data between coordinate sys- tems. For example, converting features from one coordinate system based on North American Datum (NAD) 27 to another from NAD83 causes the FME to perform the required datum conversion. To ensure that the reprojection is accurate, FME automatically vectorizes arcs, ellipses, rec- tangles, and rounded rectangle objects as necessary before performing the coordinate system change. The output system, or format, stores the coordinate system of the features if it has facilities for doing so; for example, the MapInfo formats store the coordinate system of the data. Quick Links n Changing the Default Coordinate System n Adding a Custom Coordinate System n Sharing Custom Coordinate Systems n Shared Directories n Included Grid Shift Files n Adding Grid Files n Using the CoordinateSystemSetter Transformer Coordinate Systems All FME features know about their coordinate system and, therefore, their location on the earth. An FME coordinate system contains a complete mathematical model of the conversion between a specific location on the earth and a set of coordinates. Coordinate system definitions are spec- ified by a set of parameters that define this mathematical model, including the earth model (ellipsoid or datum), the units used to measure the coordinates, the projection type, and any parameters specific to the projection type. Coordinate systems may be extracted from input feature data sources, may come predefined with the FME, or may be defined by FME users. The FME allows output coordinate systems that are different than the input ones to be specified and performs the required coordinate con- versions when necessary. FME is shipped with over 5000 coordinate systems based on a variety of different projections, ellipsoids, and datums. The file coordsys.db in the FME installation directory contains the names and descriptions of all predefined coordinate systems. However, some users may wish to use coordinate systems that do not ship with FME, and will need to read the topics on defining custom coordinate systems. When an FME reader knows its coordinate system, the FME creates a coordinate system to match the input data specification and tags each fea- ture read with this system name. However, a majority of formats do not explicitly store the coordinate system. In such cases, mapping file direc- tives are used to supply coordinate system information. The mapping file may also contain a specification as to which coordinate system the output data is to be in. If the output coordinate system is specified and it is different from the input coordinate system, then the FME automatically converts the feature data between coordinate sys- tems. For example, converting features from one coordinate system based on North American Datum (NAD) 27 to another from NAD83 causes the FME to perform the required datum conversion. To ensure that the reprojection is accurate, FME automatically vectorizes arcs, ellipses, rec- tangles, and rounded rectangle objects as necessary before performing the coordinate system change. The output system, or format, stores the coordinate system of the features if it has facilities for doing so; for example, the MapInfo formats store the coordinate system of the data. Quick Links n Changing the Default Coordinate System n Adding a Custom Coordinate System n Sharing Custom Coordinate Systems n Shared Directories n Included Grid Shift Files n Adding Grid Files n Using the CoordinateSystemSetter Transformer How FME Identifies Coordinate Systems A coordinate system is a reference system for spatial data to be related to a particular space on the Earth's surface. It is made up of a number of components such as projection (http://en.wikipedia.org/wiki/Map_projection), geoid (http://en.wikipedia.org/wiki/Geoid), datum (http://e- n.wikipedia.org/wiki/Datum) and units (http://en.wikipedia.org/wiki/Units_of_measurement). Each feature that is processed by FME is coordinate system aware; that is, it knows what coordinate system it belongs to at all times. This helps prevent confusion when reading multiple datasets that belong to different coordinate systems. When working with FME, you generally only have to consider the coordinate system if you want to reproject the data to another system or if FME fails to automatically recognize the correct coordinate system. Coordinate systems are defined in the Workbench Navigator. Because the source Reader coordinate system is marked <not set>, FME will try to determine the coordinate system from the source dataset. Because the destination Writer coordinate system is marked <not set>, FME will not reproject the data. Instead FME writes the data using the same coordinate system as the source data. Each Coordinate System parameter is linked to FME's Coordinate System Gallery. Double-click the parameter to display a list of recently used coordinate systems, or the browse button to access FME's Coordinate System Gallery. If you define the coordinate systems FME automatically restructures the data at the end of the translation, so that the output is in the correct location. How FME Processes Coordinate Systems in the Workspace If a coordinate system is specified in both the source format and the workspace, the coordinate system in the workspace is the one that will be used. The coordinate system specified in the source format is not used, and a warning is logged. If a source coordinate system is not specified in the workspace and the format or system does not store coordinate system information, then the coordinate system is not set for the features that are read. If a destination coordinate system is set and the feature has been tagged with a coordinate system, then a coordinate system conversion is per- formed to put the feature into the destination system. This happens after features leave the transformer, but before they enter the trans- formation process. If the destination coordinate system was not set, then the features are written out in their original coordinate system. If a destination coordinate system is set, but the source coordinate system was not specified in the workspace or stored in the source format, then no conversion is performed. The features are simply tagged with the output system name before being written to the output dataset. Choosing from the Coordinate System Gallery Tools > Browse Coordinate Systems Browse button beside any Coordinate System field From the Coordinate System Gallery, you can search for a keyword, filter entries, select a new coordinate system, and view properties on selected coordinate systems. Any custom coordinate systems that you add will also appear here. Changing the Default Coordinate System By default, FME either uses a default value or uses the coordinate system referenced in the input dataset. However, you may want to convert data to a different coordinate system. For formats that know their coordinate system (such as MapInfo and DLG), the Coordinate System field in the Source Dataset dialog will display Same as source and FME will read the coordinate system from the source dataset. For most other input sources, the field will display <not set>, which means that FME will use default values. For FME to perform a reprojection, you must specify different writer coordinate system parameters. Converting to a Different Writer Coordinate System 1. Create a workspace, and define your reader and writer. 2. In the source dataset area in the Navigator pane, the Coordinate System parameter will be displayed as <not set>. This means that FME will either use default values, or will read the coordinate system from the source data. You can explicitly set the source coordinate system (which will override any coordinate system read
Load more

Recommended publications
  • State Plane Coordinate System
    Wisconsin Coordinate Reference Systems Second Edition Published 2009 by the State Cartographer’s Office Wisconsin Coordinate Reference Systems Second Edition Wisconsin State Cartographer’s Offi ce — Madison, WI Copyright © 2015 Board of Regents of the University of Wisconsin System About the State Cartographer’s Offi ce Operating from the University of Wisconsin-Madison campus since 1974, the State Cartographer’s Offi ce (SCO) provides direct assistance to the state’s professional mapping, surveying, and GIS/ LIS communities through print and Web publications, presentations, and educational workshops. Our staff work closely with regional and national professional organizations on a wide range of initia- tives that promote and support geospatial information technologies and standards. Additionally, we serve as liaisons between the many private and public organizations that produce geospatial data in Wisconsin. State Cartographer’s Offi ce 384 Science Hall 550 North Park St. Madison, WI 53706 E-mail: [email protected] Phone: (608) 262-3065 Web: www.sco.wisc.edu Disclaimer The contents of the Wisconsin Coordinate Reference Systems (2nd edition) handbook are made available by the Wisconsin State Cartographer’s offi ce at the University of Wisconsin-Madison (Uni- versity) for the convenience of the reader. This handbook is provided on an “as is” basis without any warranties of any kind. While every possible effort has been made to ensure the accuracy of information contained in this handbook, the University assumes no responsibilities for any damages or other liability whatsoever (including any consequential damages) resulting from your selection or use of the contents provided in this handbook. Revisions Wisconsin Coordinate Reference Systems (2nd edition) is a digital publication, and as such, we occasionally make minor revisions to this document.
    [Show full text]
  • Implications for the Adoption of Global Reference Geodesic System SIRGAS2000 on the Large Scale Cadastral Cartography in Brazil
    Implications for the Adoption of Global Reference Geodesic System SIRGAS2000 on the Large Scale Cadastral Cartography in Brazil Vivian de Oliveira FERNANDES and Ruth Emilia NOGUEIRA, Brazil Key words: SIRGAS2000, SAD69, Global Geodesic System SUMMARY Since 2005 Brazil is going through a singular moment into Cartography. In January 2005, SIRGAS2000 began to be the geodetic official reference system for Geodesy and Cartography, with the concomitant use of SAD69. Since January 2015, only SIRGAS2000 will be official, and all cartographical products will have to be referenced into this Datum. The adoption of a geocentric reference system happens from the technological evolution that has favored an improvement of the Geodetic Reference System – SGR. Differently of a single alternative for the improvement of the SGR, the adoption of a new geocentric reference system is a basic necessity into the world-wide scenery to activities that depend on spatialized information. The technological advancements in the global positioning methods, specially in the satellite positioning systems. This change reaches more quickly the organs that need spatialized information in their infrastructure and planning activities, like town halls and services concessionaires like Telecommunications, Sanitation, Electric Energy among others, which need the real knowledge of the urban space: use and occupation of the soil, subsoil and air space, fiscal and housing technical register, generic plant of values, block plant, register reference plant, municipal master plan, among others that are derived from a cartographical basis of quality. Officially, were adopted these geodetic reference systems in Brazil: Córrego Alegre, Astro Datum Chuá, SAD69, and now SIRGAS2000. For legislation it is in transition for the SIRGAS2000.
    [Show full text]
  • Part V: the Global Positioning System ______
    PART V: THE GLOBAL POSITIONING SYSTEM ______________________________________________________________________________ 5.1 Background The Global Positioning System (GPS) is a satellite based, passive, three dimensional navigational system operated and maintained by the Department of Defense (DOD) having the primary purpose of supporting tactical and strategic military operations. Like many systems initially designed for military purposes, GPS has been found to be an indispensable tool for many civilian applications, not the least of which are surveying and mapping uses. There are currently three general modes that GPS users have adopted: absolute, differential and relative. Absolute GPS can best be described by a single user occupying a single point with a single receiver. Typically a lower grade receiver using only the coarse acquisition code generated by the satellites is used and errors can approach the 100m range. While absolute GPS will not support typical MDOT survey requirements it may be very useful in reconnaissance work. Differential GPS or DGPS employs a base receiver transmitting differential corrections to a roving receiver. It, too, only makes use of the coarse acquisition code. Accuracies are typically in the sub- meter range. DGPS may be of use in certain mapping applications such as topographic or hydrographic surveys. DGPS should not be confused with Real Time Kinematic or RTK GPS surveying. Relative GPS surveying employs multiple receivers simultaneously observing multiple points and makes use of carrier phase measurements. Relative positioning is less concerned with the absolute positions of the occupied points than with the relative vector (dX, dY, dZ) between them. 5.2 GPS Segments The Global Positioning System is made of three segments: the Space Segment, the Control Segment and the User Segment.
    [Show full text]
  • HORIZONTAL DATUM CONVERSIONS Helping Vermonters Visualize Choice
    PART 3: SECTION K HORIZONTAL DATUM CONVERSIONS Helping Vermonters Visualize Choice A Discussion, Examples, and Recommended Conversion Methodology for the Transformation of ARC/INFO Coverages from the North American Datum of 1927 to the North American Datum of 1983 in Vermont. This paper would not have been made available without the thoughtful writing of Milo Robinson, NGS Geodetic Advisor to the State of Vermont, and Gary Smith of Green Mountain Geographics. These recognized leaders in the VGIS community have all of our thanks. EXECUTIVE SUMMARY This paper outlines the steps required to convert ARC/INFO coverages from the North American Datum of 1927 (NAD27) to the more accurate North American Datum of 1983 (NAD83). Until recently, most contemporary maps of Vermont used the NAD27 as the reference datum. This made it the logical option for direct digital conversion and subsequent inclusion in the Vermont GIS database. With the arrival of the new Vermont Digital Orthophotography, expanded GPS activity and new maps from the U.S. Geological Survey being prepared using NAD83, it is increasingly necessary to convert existing NAD27 data to NAD83 to properly incorporate new information. The need of particular data developers or users to convert data depends on the location in the State, and particular mapping requirements. As this paper is released the Vermont counties for which NAD83 digital orthophotos are available are Rutland, Windsor, Franklin, Grand Isle and Addison, plus portions of Washington County. The remainder of Washington and Orange Counties will be available soon, with the remainder of Vermont to be processed in coming years. The remainder of this paper provides more detail on the datum change, suggests new data entry guidelines, details the coordinate and naming convention for Vermont's orthophotos, and provides the procedures for converting Vermont's NAD27 data to NAD83 using software by ESRI (Environmental Systems Research Institute, Redlands, CA).
    [Show full text]
  • Datums in Texas NGS: Welcome to Geodesy
    Datums in Texas NGS: Welcome to Geodesy Geodesy is the science of measuring and monitoring the size and shape of the Earth and the location of points on its surface. NOAA's National Geodetic Survey (NGS) is responsible for the development and maintenance of a national geodetic data system that is used for navigation, communication systems, and mapping and charting. ln this subject, you will find three sections devoted to learning about geodesy: an online tutorial, an educational roadmap to resources, and formal lesson plans. The Geodesy Tutorial is an overview of the history, essential elements, and modern methods of geodesy. The tutorial is content rich and easy to understand. lt is made up of 10 chapters or pages (plus a reference page) that can be read in sequence by clicking on the arrows at the top or bottom of each chapter page. The tutorial includes many illustrations and interactive graphics to visually enhance the text. The Roadmap to Resources complements the information in the tutorial. The roadmap directs you to specific geodetic data offered by NOS and NOAA. The Lesson Plans integrate information presented in the tutorial with data offerings from the roadmap. These lesson plans have been developed for students in grades 9-12 and focus on the importance of geodesy and its practical application, including what a datum is, how a datum of reference points may be used to describe a location, and how geodesy is used to measure movement in the Earth's crust from seismic activity. Members of a 1922 geodetic suruey expedition. Until recent advances in satellite technology, namely the creation of the Global Positioning Sysfem (GPS), geodetic surveying was an arduous fask besf suited to individuals with strong constitutions, and a sense of adventure.
    [Show full text]
  • Mind the Gap! a New Positioning Reference
    A new positioning reference Why is the United States adopting NATRF2022? What are we doing about this in Canada? We want to hear from you! • The Canadian Geodetic Survey and the United States • Improved compatibility with Global Navigation • The Canadian Geodetic Survey is working closely National Geodetic Survey have collaborated for Satellite Systems (GNSS), such as GPS, is driving this with the United States National Geodetic Survey in • Send us your comments, the challenges you over a century to provide the fundamental reference change. The geometric reference frames currently defining reference frames to ensure they will also foresee, and any concerns to help inform our path Mind the gap! systems for latitude, longitude and height for their used in Canada and the United States, although be suitable for Canada. forward to either of these organizations: respective countries. compatible with each other, are offset by 2.2 m from • Geodetic agencies from across Canada are A new positioning reference the Earth’s geocentre, whereas GNSS are geocentric. - Canadian Geodetic Survey: nrcan. • Together our reference systems have evolved collaborating on reference system improvements geodeticinformation-informationgeodesique. to meet today’s world of GPS and geographical • Real-time decimetre-level accuracies directly from through the Canadian Geodetic Reference System [email protected] NATRF2022 information systems, while supporting legacy datums GNSS satellites are expected to be available soon. Committee, a working committee of the Canadian
    [Show full text]
  • JHR Final Report Template
    TRANSFORMING NAD 27 AND NAD 83 POSITIONS: MAKING LEGACY MAPPING AND SURVEYS GPS COMPATIBLE June 2015 Thomas H. Meyer Robert Baron JHR 15-327 Project 12-01 This research was sponsored by the Joint Highway Research Advisory Council (JHRAC) of the University of Connecticut and the Connecticut Department of Transportation and was performed through the Connecticut Transportation Institute of the University of Connecticut. The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Connecticut or the Connecticut Department of Transportation. This report does not constitute a standard, specification, or regulation. i Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. JHR 15-327 N/A 4. Title and Subtitle 5. Report Date Transforming NAD 27 And NAD 83 Positions: Making June 2015 Legacy Mapping And Surveys GPS Compatible 6. Performing Organization Code CCTRP 12-01 7. Author(s) 8. Performing Organization Report No. Thomas H. Meyer, Robert Baron JHR 15-327 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) University of Connecticut N/A Connecticut Transportation Institute 11. Contract or Grant No. Storrs, CT 06269-5202 N/A 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Connecticut Department of Transportation Final 2800 Berlin Turnpike 14. Sponsoring Agency Code Newington, CT 06131-7546 CCTRP 12-01 15. Supplementary Notes This study was conducted under the Connecticut Cooperative Transportation Research Program (CCTRP, http://www.cti.uconn.edu/cctrp/).
    [Show full text]
  • Evolution of NAD 83 in the United States: Journey from 2D Toward 4D
    Evolution of NAD 83 in the United States: Journey from 2D toward 4D Richard A. Snay1 Abstract: In 1986, Canada, Greenland, and the United States adopted the North American Datum of 1983 (NAD 83) to replace the North American Datum of 1927 as their official spatial reference system for geometric positioning. The rigor of the original NAD 83 realization benefited from the extensive use of electronic distance measuring instrumentation and from the use of both TRANSIT Doppler observations and very long baseline interferometry observations. However, the original NAD 83 realization predated the widespread use of the global po- sitioning system and the use of continuously operating reference stations. Consequently, NAD 83 has evolved significantly in the United States since 1986 to embrace these technological advances, as well as to accommodate improvements in the understanding of crustal motion. This paper traces this evolution from what started as essentially a two-dimensional (2D) reference frame and has been progressing toward a four-dimensional (4D) frame. In anticipation of future geodetic advances, the U.S. National Geodetic Survey is planning to replace NAD 83 about a decade from now with a newer, more geocentric spatial reference system for geometric positioning. DOI: 10.1061/(ASCE)SU.1943- 5428.0000083. © 2012 American Society of Civil Engineers. CE Database subject headings: History; Datum; Transformations; Geodetic surveys; North America. Author keywords: History; Datum transformations; Dynamic datums; Crustal deformation; NAD 83. Introduction height, and how these three coordinates vary over time. NAD 27 provided a foundation for measuring only geodetic latitude and lon- In 1986 a group of institutions representing Canada, Greenland, and gitude; therefore, it is considered a horizontal datum.
    [Show full text]
  • Arcgis 10.1 Geographic and Vertical Transformation Tables
    ArcGIS 10.1 Geographic and Vertical Transformation Tables Note: Some numbers have been rounded for display. Area of use values are in degrees based upon WGS 1984. Table 1: Geographic (datum) transformations: well-known IDs, accuracies and areas of use ........................................................................................... 1 Table 2: Geographic (datum) transformations: Longitude rotation and unit change methods ......................................................................................... 43 Table 3: Geographic (datum) transformations: Geographic 2D offset method ................................................................................................................ 44 Table 4: Geographic (datum) transformations: Geocentric translation method ............................................................................................................... 44 Table 5: Geographic (datum) transformations: Coordinate frame (CF) and position vector (PV) methods .................................................................... 60 Table 6: Geographic (datum) transformations: Molodensky-Badekas method ................................................................................................................ 70 Table 7: Geographic (datum) transformations: HARN, NADCON, and NTv2 methods ................................................................................................. 71 Table 8: Geographic transformation methods: well-known IDs ......................................................................................................................................
    [Show full text]
  • Killet Software Ing.-Gbr
    History of the program TRANSDATpro Changes and Supplements of the last five years Worldwide geodetic Coordinate Transformations Detailed Information about the program TRANSDATpro: https://www.killetsoft.de/p_trda_e.htm Translation of this history to other languages: https://translate.google.com/ 01. 01. 2021: Program release TRANSDATpro 24.00 Changes and Supplements during the version TRANSDATpro 24.xx: 24.14: New help chapter "Selection of a Meridian Strip". 24.13: New round button to call the help "Selection of a Meridian Strip". 24.12: New Help link "What actually is a Coordinate Reference System?" 24.11: For calculations with the Mercator projection (1SP / 2SP) the International Date Line is considered. 24.10: New coordinate system "PDC Mercator (Pacific)". 24.10: EPSG code 3832 "WGS84 / PDC Mercator" implemented. 24.09: RefSys "ETRS89 (EU GPS measurements)" renamed to "ETRS89 (EU ITRS epoch 1989)". 24.09: RefSys "NAD83(US+CA GPS measurements)" renamed to "NAD83(US+CA ITRS epoch 1988)". 24.09: RefSys "GDA2020 (AU GPS measurements)" renamed to "GDA2020 (AU ITRS epoch 2020)". 24.08: Automatic language detection at the first program call adjusted. 24.07: Increased stability and speed with a new development system. 24.07: Delivered with new Dynamic Link Libraries (DLLs). 24.06: Error handling improved. 24.05: New NTv2 reference system for Belgium added. 24.05: New NTv2 reference systems for Portugal added. 24.03: New Language interface file for Bosnian, Croatian and Serbian added. 24.02: New language interface file for Italian added. 24.01: Restricted access to functions of the underlying GeoDLL fixed. 24.01: Link to the worldwide NTv2 files collection corrected.
    [Show full text]
  • Map Projections and Coordinate Systems Datums Tell Us the Latitudes and Longi- Vertex, Node, Or Grid Cell in a Data Set, Con- Tudes of Features on an Ellipsoid
    116 GIS Fundamentals Map Projections and Coordinate Systems Datums tell us the latitudes and longi- vertex, node, or grid cell in a data set, con- tudes of features on an ellipsoid. We need to verting the vector or raster data feature by transfer these from the curved ellipsoid to a feature from geographic to Mercator coordi- flat map. A map projection is a systematic nates. rendering of locations from the curved Earth Notice that there are parameters we surface onto a flat map surface. must specify for this projection, here R, the Nearly all projections are applied via Earth’s radius, and o, the longitudinal ori- exact or iterated mathematical formulas that gin. Different values for these parameters convert between geographic latitude and give different values for the coordinates, so longitude and projected X an Y (Easting and even though we may have the same kind of Northing) coordinates. Figure 3-30 shows projection (transverse Mercator), we have one of the simpler projection equations, different versions each time we specify dif- between Mercator and geographic coordi- ferent parameters. nates, assuming a spherical Earth. These Projection equations must also be speci- equations would be applied for every point, fied in the “backward” direction, from pro- jected coordinates to geographic coordinates, if they are to be useful. The pro- jection coordinates in this backward, or “inverse,” direction are often much more complicated that the forward direction, but are specified for every commonly used pro- jection. Most projection equations are much more complicated than the transverse Mer- cator, in part because most adopt an ellipsoi- dal Earth, and because the projections are onto curved surfaces rather than a plane, but thankfully, projection equations have long been standardized, documented, and made widely available through proven programing libraries and projection calculators.
    [Show full text]
  • FDM 9-20 Spatial Reference Systems
    Facilities Development Manual Wisconsin Department of Transportation Chapter 9 Surveying and Mapping Section 20 Spatial Reference Systems FDM 9-20-1 General February 28, 2001 The discipline of surveying consists of determining or establishing relative positions of points above, on, or beneath the surface of the earth. In Wisconsin, there are two primary spatial reference systems for defining the location of a point: - The U.S. Public Land Survey System (PLSS). - The National Spatial Reference System (NSRS). The PLSS is based on a system of townships, ranges, and sections (see FDM 9-20-5). The PLSS provides the basis for almost all legal descriptions of land. The NSRS, which includes the former National Geodetic Reference System (NGRS), is a mathematical reference system (see FDM 9-20-10). The NSRS consists of precisely measured networks of geodetic control that support accurate mapping over large areas. To understand the roles of these reference systems, it is important to recognize that the PLSS was designed for land ownership purposes but not for accurate mapping, and the NSRS was designed for geodetic surveying and mapping but not for land ownership documentation. Since accurate property maps are becoming essential with digital-based ownership documents, it is important that there be a substantial link between the two reference systems. Methods are needed to utilize the spatial characteristics of the NSRS when addressing the location of landmarks. Fortunately, recent technological developments such as the Global Positioning System (GPS), electronic total station survey instruments, and computer aided drafting (CAD) now make the task of using the PLSS and NSRS together more efficient, economical, and practical.
    [Show full text]