convert nad27 to wgs84 formula convert nad27 to wgs84 formula

For example, USGS topographic maps generally were published using a NAD27 datum. Log in . When combining data from different users or eras, it is important to transform all information into common geodetic datums. Any you already have installed. The NAD27 datum was based on the Clarke Ellipsoid of 1866: The NAD83 datum was based on the Geodetic Reference System (GRS80) Ellipsoid: When you transform NAD83 and NAD27 geographic coordinates to projected State Plane coordinates, it is the same projection method. The North American Datum of 1927 (NAD27) is one of the main three geodetic datums in North America. To convert into various coordinate formats, we freely offer our Excel template. Datums precisely specify each location on Earths surface in latitude and longitude. Turn off on-the-fly transformations for you project and load the saved NAD27(BLM14) file in. Copyright 2000-2023 Groundspeak, Inc. DBA Geocaching. Connect and share knowledge within a single location that is structured and easy to search. Here is the spatial reference list. ", "Transformation steps are from NAD27 to NAD83(HARN) (12) (code 8471) assuming that NAD83(HARN) is equivalent to WGS 84 within the accuracy of the transformation. A common problem is when different coordinate locations are stored in different reference systems. Contents of the Free Geography Tools Blog copyright 2007-2018; all rights reserved. You'll want to use some third party tools to do the transform. NGS Coordinate Conversion and Transformation Tool (NCAT) Convert/Transform from: Horizontal+height Select the type of horizontal coordinate: + Leaflet | Sources Esri, DeLorme, HERE, USGS, Intermap, iPC, NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, and the GIS User Community Enter lat-lon in decimal degrees Lat Lon For all practical applications, NAD83 is the same as WGS84. DWalsh wrote: > > Hi Rod, > This version was intended to be geocentric and used the GRS80 ellipsoid. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Most overview landmarks have not moved. Reference codes may be found at spatialreference.org. As of September 2000, the grids for 44 states and two territories had been published. How accurate do you need the transform? Your email address will not be published. Canadas standard transformation program between NAD27 and NAD83 was developed by the Canadian Geodetic Survey. The link is as follows: http://webapp.geod.nrcan.gc.ca/geod/ Conclusion Available transformations. Canada - Quebec. At a geodetic or ellipsoidal height h, . For any type of work where coordinates need to be consistent with each other, you must use the same geodetic datum. Having failed to recently update I delete them attempted to download again. Surveyors could measure any point with a latitude and longitude away from this reference point based on the Clarke Ellipsoid of 1866. SPCS83 (Version 2.1) Converts NAD 83 State Plane Coordinates to NAD 83 geographic positions (latitudes and longitudes) and vice versa. The average correction between NAD27 and NAD83 is an average of 0.349 northward and 1.822 eastward. Convert from NAD83 to WGS84 is real fast and easy. Converting a NAD27 Lambert Conformal Conic custom projection to WGS84 using QGIS. What sort of strategies would a medieval military use against a fantasy giant? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Lightweighted projection library https://github.com/proj4js/proj4js. I suspect the group that originated the app got bought out or has disbanded. . NAD27 is the adjustment of long-baseline surveys. This converts between NAD27 and NAD83 (1986) using the NADCON transformation. you should have the on-the-fly projection setting turned on this could be the answer to the discrepancy question. This effort, known as HARN or HPGN, is a cooperative project between the National Geodetic Survey and individual states. Thanks in advance. Therefore, the NADCON computed transformations are extrapolations and no accuracy can be stated.. 10 Topographic Maps From Around the World, Ocean Currents Map: Visualize Our Oceans Movement, Esri JavaScript API Examples: 15 High-Tech Webmaps and Webscenes, 50 Map Projections Types: A Visual Reference Guide [BIG LIST]. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? datums. Transformations between old datums (NAD27, Old Hawaiian, Puerto Rico, etc.) It was a purchased app but recently failed to update. But now I cant find it when I search within my apps. Is there a proper earth ground point in this switch box? Clear editor. Depending on where you are in North America, NAD27 and NAD83 may differ in tens of meters for horizontal accuracy. Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). Where is your data geographically located? Can I tell police to wait and call a lawyer when served with a search warrant? This has led to the development of global ellipsoid models such as WGS72, GRS80, and WGS84 (current). I don't need to be perfect. The latitude and longitude location in the NAD27 datum differs from NAD83 or WGS84. Geodesists use a horizontal datum as the model to translate a spheroid/ellipsoid into locations on Earth with latitude and longitude lines. En el botn select coordinate System elegimos el sistema de orgen. Do you guys know any resources in or outside of tableau that I can use to convert a bunch of state planes to lat/long? Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. Surly Straggler vs. other types of steel frames. Read More. And since the beginning of the 19th century, the dimensions of the ellipsoid have been calculated at least 20 different times with considerably different accuracy. In the top box, select NAD27 if it isn't. Does anyone know how to do this or where I can find examples on the web? You can also use command line utilities to convert your coordinates: One way to use gdaltransform is to start a terminal session (OSGeo4W if you are on Windows) and interactively execute: EPSG stands for European Petroleum Survey Group. The datum was redefined and recomputed, resulting in NAD83, which is . Your link has been automatically embedded. Hi, looks like the Cartisan Total Map Coordinate Converter is no longer available from the website (actually, the whole sites down) Find a coordinate system and get position on a map. This would be acceptable for my purposes. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. This compares to the Clarke ellipsoid with a semi-major axis of 6,378,206.4 m and a semi-minor axis of 6,356,583.8 meters. Cartisan Total Map Coordinate Converter does anybody have the Marco for this spreadsheet. Method: NADCON The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup, On the fly transformation From WGS84 to NAD27 with proj4 code, Transform from WGS84 to Cylindrical Equal Area, Transform coordinates in csv file from wgs84 to nad27 using qgis, Troubleshooting the use of OpenLayers Plugin layers with Midvatten Plugin in QGIS. Earth bulges out more at the equator than at the poles by about 70,000 feet. If you want to use PHP, you could use Proj4PHP. You can also convert coordinates using many other spatial references. Over time, surveyors have gathered a massive collection of surface measurements to more reliably estimate the ellipsoid. WGS84 frames are specifically named NAD83 (CORS96) and WGS84 (G1150). The best method these days is using distortion models which I believe is used with things like NADCON, http://www.ngs.noaa.gov/TOOLS/Nadcon/Nadcon.html. A datum describes the shape of the Earth in mathematical terms. http://everest.hunter.cuny.edu/mp/software.html Therefore, the Nadcon computed transformations are extrapolations and no accuracy can be stated." Thanks, Rod. Nearly all published statements about the amount of shift between NAD27 and NAD83 are shifts measured in meters on unprojected (latitudelongitude) data. Input the coordinates in a decimal degrees (DD) format. Enter your coordinate data in the areas highlighted in green in the spreadsheet. Connect and share knowledge within a single location that is structured and easy to search. In near offshore regions, results will be less accurate but seldom in excess of 5.0 m. Farther offshore, NAD27 was undefined. A coordinate transformation is a conversion from a non-projected coordinate system to a coordinate system. This conversion generally is accurate within about 0.5 feet for 95 percent of the study area. Macro/VBA to add text from another cell into current cell when I type a certain value. The latitudes and longitudes of every other point in North America were based on its direction, angle, and distance away from Meades Ranch. Where does this (supposedly) Gibson quote come from? In surveying and geodesy, we accurately define these properties with geodetic datums. In near offshore regions, results will be less accurate, but seldom in excess of 5.0 meters. If you are converting to or from state plane, use the NAD27 keyword instead. For example, surveyors benchmarked approximately 250,000 stations. Remarks: Transformation steps are from NAD27 to NAD83 (HARN) (12) (code 8471) assuming that NAD83 (HARN) is equivalent to WGS 84 within the accuracy of the transformation. Or convert them to any other coordinate I can map onto tableau. - Conversion of Coordinates in Decimal Degrees to UTM. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? The mapping platform for your organization, Free template maps and apps for your industry. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Projected coordinate systems are based on geographic coordinates, which are in turn referenced to a datum. Coordinates on a map A horizontal datum provides a frame of reference as a basis for placing specific locations at specific points on the spheroid. 9874) instead of degrees, minutes, and seconds (-73 59' 14. . What video game is Charlie playing in Poker Face S01E07? I've been asked by some users of my Spreadsheet if i could add the the conversion from WGS84 to NAD27. Chris, try this link out http://www.gpsu.co.uk/. How to convert WGS84 to NAD27 in pygeodesy? I'm trying to fix NAD27 points on Google maps as they're all off by like 150 ft. The default NAD27 to WGS84 transformation is NAD_1927_To_WGS_1984_1, . Click Open Map (appears after the end of the conversion) to visualize the converted coordinates on the World map. For example, EPSG:4326 and EPSG:4267 are reference codes for WGS84 and NAD27, respectively: will return the corresponding coordinate in NAD27. JavaScript is disabled. Points in other parts of the world will coincide, as there is no offset definition for them. United States (USA) - Delaware and Maryland. All Rights Reserved. For convenience, a link is included to the National Geodetic Survey's NADCON program, which allows conversions between the NAD83 / WGS84 coordinate system and the older NAD27 coordinate system. Thanks for contributing an answer to Geographic Information Systems Stack Exchange! However, NAD83 is not geocentric with an offset of about two meters. The state plane projection will not allow you to use the datum keywords OLD_HAWAIIAN or ALASKAN_ISLAND. 10 comments caleb87 commented on Oct 5, 2016 proj4php/proj4php#53 Using QGIS, I loaded my shapefile into one layer and set the CRS to WGS84, then I loaded the same data again and set its layer to NAD27. At each station, surveyors collected latitudes and longitude coordinates. All input and output linear units are in meters. a mammoth collection of monument locations, mathematical techniques like triangulation, NOAAs National Geodetic Survey used these survey stations and triangulation. Your email address will not be published. Get your coordinates in the WGS84 on your display. Linear Algebra - Linear transformation question. NADCON, an acronym for North American Datum Conversion, is a datum transformation program created by the U.S. National Geodetic Survey (NGS). . It appears after finishing the conversion process. How can I take a NAD27 decimal coordinate like 39.748303,-104.998634 and convert it to NAD83 or WGS84 with a programming function in PHP or JS? Earth bulges out more at the equator than at the poles by about 70,000 feet. The National Geodetic Survey relied heavily on the use of the Doppler satellite to locate the Earths center of mass. The NAD27 datum was based on the Clarke Ellipsoid of 1866: The NAD83 datum was based on the Geodetic Reference System (GRS80) Ellipsoid: For any type of work where coordinates need to be consistent with each other, you must use the same geodetic datum. Area of use: United States (USA) - Delaware and Maryland. For example, ArcMap has seven formulas that convert from NAD27 to NAD83. The following projection file converts an NAD27 dataset to an NAD83 dataset: The following keywords (and associated regional coverage) are valid datum names when using the NADCON method for datum transformation. A geographic coordinate system (GCS) is a coordinate system associated with positions on Earth (geographic position). The best answers are voted up and rise to the top, Not the answer you're looking for? We reference all coordinates to a datum. In order to create a geodetic datum, surveyors undertook a mammoth collection of monument locations in the late 1800s. The currently accepted method is an error averaging, rubbersheeting approach. In areas of sparse geodetic data coverage, NADCON may yield less accurate results but seldom in excess of 1.0 m. Transformations between NAD83 and the States/Regions with High Accuracy Reference Networks (HARN) introduce approximately 0.05 m uncertainty. We begin modeling the Earth with a sphere or ellipsoid. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. For example, USGS topographic maps generally were published using a NAD27 datum. En este ejemplo, yo tengo un mapa en NAD27, entonces elegimos este sistema en el botn select coordinate system; este deseo pasarlo a NAD83, este se lo asigno en el siguiente botn del mismo panel (source drawing). Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Not really. The best answers are voted up and rise to the top, Not the answer you're looking for? It only takes a minute to sign up. To learn more, see our tips on writing great answers. Never before have we been able to estimate the ellipsoid with such precision because of the global set of measurements provided by GPS. How to Convert Coordinates using ExpertGPS Step 1: Configure your input and output coordinate formats To add a coordinate format in ExpertGPS, click Preferences on the Edit menu, and click on the My Coordinate Formats tab. Have you research the problem? You can open imagerywith a world file. Depending on where you are in North America, NAD27 and NAD83 may differ in tens of meters for horizontal accuracy. North American Datum of 1983 is based on the reference ellipsoid GRS80 which is physically larger than NAD27s Clarke ellipsoid. (PHP Syntax), From an array of objects, extract value of a property as array. No plugin or software installation is required for you.. Powered by Aspose.GIS. Conversions between NAD27 and NAD83. This would be acceptable for my purposes. your ~ 50 meters. This difference is known as a datum shift. Am I missing something obvious? Sad to see it disappear. A datum defines the following parameters for an ellipsoid: The North American datum of 1983 (NAD83) is the current horizontal or geometric datum for the United States. Also, it happens when there are more of them and methods of geodesy change. If you have an account, sign in now to post with your account. Because we created maps using different geodetic datums throughout history, datum transformations are often necessary when using historical data. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The average correction between NAD27 and NAD83 is an average of 0.349 northward and 1.822 eastward. It is known locally as the National Transformation and will be referred to in this document and the software as the Canadian National Transformation. Actually, because of these changes, there is more than one version of NAD83. Because maps were created in different geodetic datums throughout history, datum transformations are often necessary. convert nad27 to wgs84 formula June 5, 2022 5:15 pm seaworld san antonio birthday party seaworld san antonio birthday party GPS (Global Positioning System), and many other applications use the ellipsoid and datum of WGS84 instead of earlier datum. convert nad27 to wgs84 formula. Depending on where you are in North America, NAD27 and NAD83 may differ in tens of meters for horizontal accuracy. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Assuming your original coordinates are actually WGS84, you just assigned an erroneous CRS of NAD27 (BLM14) the second time you imported the data. In this case, you would need to perform a datum transformation. You cannot convert between Old Hawaiian or Alaskan Island and NAD27 because NADCON does not have the necessary information. Making statements based on opinion; back them up with references or personal experience. The following statement is from the release notes of NADCON Version 2.1, October 1993: The accuracy of the transformation should be viewed with some caution. If you are marking property boundaries, building roads, or planning for coastal inundation scenarios, you must know about and use the correct geodetic datums. NAD27 to HARN equals 0.15m + 0.05m = 0.20m). The horizontal datums that form the basis of coordinates of all horizontal positions in North America improve. Then select Nadcon (NGS) from the Type option list. Scope: (null/copy) Approximation for medium and low accuracy applications assuming equality between plate-fixed static and earth-fixed dynamic CRSs, ignoring static/dynamic CRS differences. Please see the popular list below. Disconnect between goals and daily tasksIs it me, or the industry? The total appears in bottom right of Excel screen. Asking for help, clarification, or responding to other answers. Making Maps: A Visual Guide to Map Design for GIS Users can select different grids by clicking on the "select grid" link below. The normal revision somewhere in the range of NAD27 and NAD83 is a normal of 0.349 northward and 1.822 eastbound. The World Geodetic System (WGS) is a standard used in cartography, geodesy, and satellite navigation including GPS.The current version, WGS 84, defines an Earth-centered, Earth-fixed coordinate system and a geodetic datum, and also describes the associated Earth Gravitational Model (EGM) and World Magnetic Model (WMM). You cannot paste images directly. I tried in gdal, How Intuit democratizes AI development across teams through reusability. Making statements based on opinion; back them up with references or personal experience. Bessel 1841 was used before Clarke 1866 was adopted because it was based on observations of triangulation arcs of North America. Surveyors gathered approximately 26,000 stations in the United States and Canada. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? I have around 10,000 coordinates . ", "(null/copy) Approximation for medium and low accuracy applications assuming equality between plate-fixed static and earth-fixed dynamic CRSs, ignoring static/dynamic CRS differences. MERCEDES Not the answer you're looking for? Has 90% of ice around Antarctica disappeared in less than a decade? It provides latitude and longitude and some height information. The first sentence you wrote perhaps is wrong that the lat long taken from Google maps are not in WGS84 rather they are in NAD27. And even today, people continue to change geodetic datums in an effort to make them more accurate. Convertir coordenadas UTM NAD27 a WGS84 en ArcGIS - YouTube 0:00 / 6:33 Introduccin Convertir coordenadas UTM NAD27 a WGS84 en ArcGIS ngel A. Gonzlez 35 subscribers Subscribe 36. (I never took any GIS classes in school, and I've only been working at this for a few weeks.). (391326.686 north latitude, 983230.506 west longitude). GIS: Convert NAD27 to WGS84 with programming function like PHP (2 Solutions!!) Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, var functionName = function() {} vs function functionName() {}, Reference Guide: What does this symbol mean in PHP? From the unified network of survey monuments, the result of triangulation was the North American Datum of 1927 (NAD 27). How to notate a grace note at the start of a bar with lilypond? This results in more accurate geodetic datums over time. ", "United States (USA) - Delaware and Maryland. Using this app is a fast and easy way to get coordinates in the WGS84 by automatically converting the coordinates of any Spatial Reference System (SRS) or EPSG code. For example, the latitude and longitude location in a NAD27 datum differs from that same benchmark in NAD83 or WGS84. These points are in West Texas, where NAD27 differs from WGS84 by about 50 meters. Especially, this is true when using historical data. However, many of you might have automated your original data layers using NAD27 and continue to do so, primarily because some source data is collected from maps based on NAD27. November 18, 2021 | | premier league goalkeeper rules | crewe homecoming 2021 Open Source GIS: A GRASS GIS Approach - Page ii UTM <-> Latitude/Longitude online converter Convert nad27 to decimal degrees" Keyword Found Websites . your input in NAD27 39.748303,-104.998634. When you do click on the datum, it shows various parameters that it uses. Your email address will not be published. If you have questions about obtaining a more reliable transformation in major urban centers or other areas that are densified, contact ESRI Canada Limited for further details. Choose lat long, decimal degrees, UTM, or state plane coordinates as your input format. Or is there a QGIS or (better) an OSGeo solution? Obviously change the reference to suite. The Global Positioning System (GPS) references the World Geodetic System (WGS84) as its coordinate reference system. The coordinates for benchmark datum points are typically different between geodetic datums. Before the current datum was defined, many maps were created using different starting points. Unfortunately, NAD 83 is not the only datum youll encounter. NOAAs National Geodetic Survey used these survey stations and triangulation to form the NAD27 datum. Can I tell police to wait and call a lawyer when served with a search warrant? I have an issue going on the pro4js github: You absolutely right about the issue that proj4js does not have a datum shift grid function included. It is suitable for the United States, Puerto Rico, and the Virgin Islands but only for conversion between the NAD27, NAD83, High Precision GPS Network (HPGN) readjustment of NAD83, and selected local island datums discussed below. Is it correct to use "the" before "materials used in making buildings are"? File is in the .RAR compression format; if your unzipping program cant handle that, try 7-Zip. This is a result of the difference between the size and origin of the two spheroids on which the data is being projected. A geodetic datum uniquely defines all locations on Earth with coordinates. The hour between square brackets is compulsory to display a. How to transform data points from WGS84 to NAD27? If so then it does the transformation for you. Click Transform to quickly convert coordinates. You can help keep this site running by allowing ads on MrExcel.com. The North American Datum of 1983 (NAD83) is the most current datum in North America. Note: Your post will require moderator approval before it will be visible. The Army and USGS references are obsolete. Thanks! Select the Input SRS (the default format is WGS84). Surveyors connected each monument location using mathematical techniques like triangulation. I work offshore and dont always have a good internet connection with which to update my apps so I do that from good WiFi before departure. Makes no sense to me but perhaps it will help you. This datum uses the Clarke Ellipsoid of 1866 with a fixed latitude and longitude at Meades Ranch, Kansas. For example, the National Geodetic Survey has adjusted the NAD83 datum four times since the original geodetic datum estimation in 1986. The tasks of conversion include: WGS84 is intended for global use. How to tell which packages are held back due to phased updates. Open data frame properties, select the coordinate system tab, click the Transformations button on the right side. The early attempts at measuring the ellipsoid used small amounts of data and did not represent the true shape of the Earth. Where does this (supposedly) Gibson quote come from? About an argument in Famine, Affluence and Morality. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Find centralized, trusted content and collaborate around the technologies you use most. Because the Earth is curved and in GIS we deal with flat map projections, we need to accommodate both the curved and flat views of the world. Aqu pueden convertir las coordenadas UTM de NAD27 A WGS84 y viceversa: http://www.xpmexico.com/index.php?module=xpcoord&func=displayresults Douglas Buitrago noviembre, 2012 at Mucho Bla Bla y nadie sabe como convertir wgs84 a nad27 o biceversa ???? Area of use: United States (USA) - Delaware and Maryland. An example is 52 12. This converter applet will convert a single pair of UTM coordinates to latitude/longitude using formulas and constants for the North American Datum of 1927 (NAD27, Clarke Ellipsoid of 1866). Comments are currently closed; feel free to contact me with questions/issues. I'll investigate the information you have all provided and see if it helps. But where can I find the origin alignment, axis rotation, and scale information that will allow me to relate Clarke 1866, GRS80, and WGS84? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This set of horizontal positions formed the basis for the North American Datum of 1983 (NAD83). Nad2Nad may be the simplest to understand (source wise), but it is not the most precise. NAD27 was not used officially in Hawaii or the Alaskan islands. Should I use the NADCON converter at http://www.ngs.noaa.gov/cgi-bin/nadcon.prl to convert my WGS84 coordinate data to NAD27? NAD27 uses all horizontal geodetic surveys collected at this time using a least-square adjustment. Transformations between old datums (NAD27, Old Hawaiian, Puerto Rico, etc.) Pasted as rich text. I am looking for a programming function that can convert NAD27 coordinates to WGS84. Files are in Microsoft Excel format, but seem to work fine in OpenOffice 2.4. Your email address will not be published. November 18, 2021 called a datum transformation (or coordinate system transformation). Surly Straggler vs. other types of steel frames. The Add Coordinate Format dialog will appear. When you combine these measurements, we arrive at a geodetic datum. For application in Gulf of Mexico refer to IOGP report 373-26. For a better experience, please enable JavaScript in your browser before proceeding. Do new devs get fired if they can't solve a certain bug? After you get two sets of coordinated in a common datum, there are three steps to get them in alignment: Remember next time in ArcMap when you use the project tool. From the unified network of survey monuments, the result of triangulation was the North American Datum of 1927 (NAD 27). In 1983, surveyors eventually replaced the NAD27 with NAD83. Making statements based on opinion; back them up with references or personal experience. GDAL/OGR are fairly robust and open source that are made for this. In case you have coordinates in CSV file somewhere online, you can call this request: Thanks for contributing an answer to Geographic Information Systems Stack Exchange! Why do small African island nations perform better than African continental nations, considering democracy and human development? Map Tools was a great little app and I used it quite a bit, especially for datum transforms. Datum shifts happen because survey measurements improve, there are more of them and methods of geodesy change. Asking for help, clarification, or responding to other answers. You would need to apply a datum transformation when working with NAD83 data. Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals.