# What projection to use in ArcMap for a map that extends over Wgs84 Utm31 and 32

Please i have a Wgs84 Utm map that extends over 2 utm zones(31N and 32N). Using either of them distorts my map and ArcGIs allows you to choose only one projection per map. Please what can i do? Thank you.

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What is your latitude? – gm70560 May 21 '13 at 23:31
These are the extents of my map in wgs84 utm(google earth). 798620.27 m E 704318.79 m N 211550.28 m E 704036.68 m N 798741.57 m E 661236.94 m N 211196.48 m E 661001.82 m N – Andy May 22 '13 at 18:14
Andy, it is numerically impossible to have a UTM map that spans UTM zones, as the coordinates reset to 0 (or whatever the projection origin and offset is) for each zone -- the coordinates are duplicated in each. You have 3 valid answers or routes to answers here, but they will take time to study and understand. Coordinate systems and projection is hard, that's why projection tag has ~500 questions, many with high ratings. The Esri documentation pointed to by TsvGis would be a profitable starting point. – matt wilkie Jun 3 '13 at 22:35

If you're just looking at displaying the data and since neighboring zones have some overlap (1 degree), you may consider reprojecting the zone with the least amount of data - pending there isn't too much of a spread. Note that is there is too much spread this method will introduce distortion which could affect areal calculations.

Alternatively, since your data spans multiple zones you might consider using a projection that is zone independent - you can choose something simple like WGS 1984 World Mercator, which is available under Projected Coordinate Systems > World in ArcGIS.

If you provide a more defined area of interest (or picture of the data) someone may be able to offer a more location-specific solution.

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Thank you for your answer.These are the extents of my map in wgs84 utm(google earth). 798620.27 m E 704318.79 m N 211550.28 m E 704036.68 m N 798741.57 m E 661236.94 m N 211196.48 m E 661001.82 m N. I hope this will help. Thank you. – Andy May 22 '13 at 7:36

If you are planning on showing a grid on top of your map, Radar's suggestions would suit the situation. If you don't need to show any grid, I would just leave the projection as geographicals WGS84.

Additionally here is the link to Esri's Help 10.1 on the issue. Crossing map projection zones

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I want my map in meters. I want it in WGS84 UTM. – Andy May 22 '13 at 18:14

Others have already given valid answers depending on what it is exactly you need. For whats it is worth, you could reproject both data sets to Transverse Mercator with a custom central meridian that lies directly on the mid-line between the two. Or, if you are working with data in high northerly latitudes you could simply reproject both to Lambert Conformal Conic which does better for data elongated East-West like you have here.

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Thank you for your answer.These are the extents of my map in wgs84 utm(google earth). 798620.27 m E 704318.79 m N 211550.28 m E 704036.68 m N 798741.57 m E 661236.94 m N 211196.48 m E 661001.82 m N Please tell me how to get the value of the central meridian that lies on the mid-line between the two. Thank you. – Andy May 22 '13 at 7:35
Which UTM zone are those coordinates in? 31N or 32N? – Mintx May 22 '13 at 21:42
The first and the third are in utm zone 31N. The 2nd and the 4th are in utm zone 32N. Thank you for your response. 798620.27 m E 704318.79 m N(utm zone 31N) 211550.28 m E 704036.68 m N(utm zone 32N) 798741.57 m E 661236.94 m N(utm zone 31N) 211196.48 m E 661001.82 m N(utm zone 32N) – Andy May 23 '13 at 21:16

As mentioned in the above post, assign GCS "WGS 84" to your ArcGIS map document for best result.

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