<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
span.EmailStyle18
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:383871872;
mso-list-type:hybrid;
mso-list-template-ids:-1639317178 67698703 67698713 67698715 67698703 67698713 67698715 67698703 67698713 67698715;}
@list l0:level1
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level2
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level3
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
@list l0:level4
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level5
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level6
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
@list l0:level7
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level8
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level9
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
ol
{margin-bottom:0in;}
ul
{margin-bottom:0in;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>I have been taking part in a discussion on another GIS list about coordinate systems, projections and transformations. This all stemmed from a person that had data which was reported to be in one coordinate system but was not overlaying other information in the same area and coordinate system. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>My experience has shown me this is not an uncommon occurrence. It seems that many GIS users do not understand how to properly project data from one coordinate system to another. I believe this is largely because they work primarily in a single local area with their own data. It is only now with the advent of services like ArcGIS Online and Google Earth combined with an increased need to coordinate activities with multiple agencies that it is now becoming more common place to share and use data from outside sources which may be in different coordinate systems and projects. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Because many GIS users have not had experience projecting data from one coordinate system to another, they choose the wrong tool or method. Instead of actually projecting the data, they instead just assign it the new or desired coordinate system using the Define Projection tool or just change the Coordinate system under the Shapefile or Feature Class properties believing this projects the data from one coordinate system to another. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Neither of these method actually project data from one coordinate system to another. All it does is change the coordinate system ArcGIS or other software packages believes the data is in. Which leads to more headaches and data displaying in the wrong location. Sadly if a user has done this with all of their data, they may believe it is correct because it appears to properly overlay itself. It is only when you try to add data from outside sources that the problem may become apparent.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>So what do you do if you get data that has been assigned the wrong coordinate system because someone used one of the methods mentioned above? Assuming you are using ArcGIS, here is my method for fixing issues like this. There is no real automated way to do this.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Delete the projection and coordinate system for the Feature Class or Shapefile that is questionable<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Open a blank map and add the above mentioned data. You will get a warning about it missing a spatial reference. That is ok. It is what you should see.<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Look at the coordinates you see as you move your mouse in the map display. See if they look similar to other values for data you work with that has a properly assigned coordinate system. If they are in the 0,0 or 5000,5000 or 10000,10000 range, then it is possible the data is not georeferenced at all and will need to be using another process. This often happens with data that was created by surveyors or engineers and converted from CAD.<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>4.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>If you identify some existing data that you think may match your questionable data, add it as a layer. If they align, then you have identified the correct coordinate system for your questionable data. If not time to move to trial and error method.<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>5.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>With the data you added above that is in an established and verified coordinate system, start changing the coordinate system to the data frame until you get the questionable data and the known data to line up. I would recommend starting with the following:<o:p></o:p></p><p class=MsoListParagraph style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>a.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Local State Plane NAD 83 (original NAD 83 not HARN, CORS 96, 2011)<o:p></o:p></p><p class=MsoListParagraph style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>b.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Local State Plane NAD 83 variants also try different Units<o:p></o:p></p><p class=MsoListParagraph style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>c.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Local State Plane NAD 27<o:p></o:p></p><p class=MsoListParagraph style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>d.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Local UTM Zone<o:p></o:p></p><p class=MsoListParagraph style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>e.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Geographic WGS 84 (especially if data was captured with GPS)<o:p></o:p></p><p class=MsoListParagraph style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>f.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Web Mercator Auxiliary Sphere<o:p></o:p></p><p class=MsoListParagraph style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>g.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Start running through any other coordinate systems commonly used in your area<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span style='mso-list:Ignore'>6.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Once you have identified the coordinate system, use the Define Projection tool to assign the correct coordinate system to the data in question.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>If your data is not Georeference or you are unable to determine the actual coordinate system for the data in question, then you will need to go through a process to georeference it. The process will depend on the type of data you have to work with. CAD and Raster data use the Georeferencing toolbar. Geodatabase Feature Classes and Shapefiles use the Spatial Adjustment toolbar. I may explain those processes in the future.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>For those that encounter georeferenced data that has been assigned the wrong coordinate system, I hope this helps.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b><i><span style='font-size:12.0pt;color:black'>Tripp Corbin, MCP, CFM, GISP</span></i></b><b><span style='font-size:12.0pt;color:black'> </span></b><span style='font-size:12.0pt;color:black'>| Chief Executive Officer</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><br></span><b><span style='font-size:18.0pt;font-family:"Times New Roman","serif";color:#1F4E79'><a href="http://www.egisassociates.com/"><span style='color:#1F4E79;text-decoration:none'>eGIS Associates, Inc.</span></a></span></b><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='color:black'><a href="mailto:tcorbin@egisassociates.com"><span style='color:blue'>tcorbin@egisassociates.com</span></a> | <a href="www.egisassociates.com"><span style='color:blue'>www.egisassociates.com</span></a> <o:p></o:p></span></p><p class=MsoNormal><span style='color:black'>678-710-9710 ext 21 | 866-</span><span lang=EN>304-3864 Fax</span><span style='color:black'><o:p></o:p></span></p><p class=MsoNormal><span style='color:black'>Esri Certified Trainer | Esri Certified Desktop Associate | Esri Certified Enterprise System Design Associate</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:black'><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>