<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; ">Hey,</div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><br></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; ">I am not sure that proj.4 is converting latitude and longitude into Hotine Oblique Mercator <span style="font-size: 12pt; ">coordinates correctly. (But I am a newbie at cartography and such, so please bear with me, I could be making a mistake.)</span></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><br></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; ">As a result of the 2010 census in the USA, many states have redrawn their congressional districts. Michigan is one, and the shapefiles for their new districts were created
using the Hotine Oblique Mercator projection to get the whole state onto one map with a minimum of overall distortion. There is a map and explanation here:</div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><br></div><div><font face="arial, helvetica, sans-serif">http://www.michigan.gov/documents/DNR_Map_Proj_and_MI_Georef_Info_20889_7.pdf</font><br></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><br></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; ">One can download Michigan's new Congressional district shapefiles from here:</div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><br></div><div><font face="arial, helvetica, sans-serif">http://www.mcgi.state.mi.us/mgdl/?rel=thext&action=thmname&cid=9&cat=Legislative+Districts+2010+US+Congress</font><br></div><div><font face="arial, helvetica,
sans-serif"><br></font></div><div><font face="arial, helvetica, sans-serif">The included prj file has this info:</font></div><div><font face="arial, helvetica, sans-serif"><br></font></div><div><font face="arial, helvetica, sans-serif"><div>PROJCS["NAD83 / Michigan Oblique Mercator",</div><div>GEOGCS["NAD83",</div><div> DATUM["North_American_Datum_1983",</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>SPHEROID["GRS 1980",6378137,298.257222101,</div><div><span class="Apple-tab-span" style="white-space:pre"> </span> AUTHORITY["EPSG","7019"]],</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>AUTHORITY["EPSG","6269"]],</div><div> PRIMEM["Greenwich",0,</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>AUTHORITY["EPSG","8901"]],</div><div> UNIT["degree",0.01745329251994328,</div><div><span class="Apple-tab-span" style="white-space:pre">
</span>AUTHORITY["EPSG","9122"]],</div><div> AUTHORITY["EPSG","4269"]],</div><div>UNIT["metre",1,</div><div> AUTHORITY["EPSG","9001"]],</div><div>PROJECTION["Hotine_Oblique_Mercator"],</div><div>PARAMETER["latitude_of_center",45.30916666666666],</div><div>PARAMETER["longitude_of_center",-86],</div><div>PARAMETER["azimuth",337.25556],</div><div>PARAMETER["rectified_grid_angle",337.25556],</div><div>PARAMETER["scale_factor",0.9996],</div><div>PARAMETER["false_easting",2546731.496],</div><div>PARAMETER["false_northing",-4354009.816],</div><div>AUTHORITY["EPSG","3078"],</div><div>AXIS["X",EAST],</div><div>AXIS["Y",NORTH]]</div><div><br></div><div>This page has info on the <span style="font-size: 16px; ">Hotine Oblique Mercator:</span></div><div><span style="font-size: 16px; "><br></span></div><div>http://www.remotesensing.org/geotiff/proj_list/hotine_oblique_mercator.html<br></div><div><br></div><div>Using that, I came up with
this command to invoke proj:</div><div><br></div><div><div>proj +proj=omerc +lat_0=45.30916666666666 +lonc=-86 +alpha=337.25556 +k_0=0.9996 +x_0=2546731.496 +y_0=-4354009.816</div><div><br></div><div>I get a latitude and longitude for Ann Arbor Michigan of 42 15 N - 83 45 W here:</div><div><br></div><div>http://wiki.answers.com/Q/What_is_the_latitude_and_longitude_of_ann_arbor_mi<br></div><div><br></div><div>Plugging 42d15N 83d45W into proj, I get -7945305.71 17799792.28. But the bounding box of the entire state's shape file is this:</div><div><br></div><div>161318.17712499946, 128066.04250000045, 791832.2827499993, 859206.8181249984<br></div><div><br></div><div>The values I get from proj are both out of bounds. </div><div><br></div><div>Am I doing something wrong?</div><div><br></div><div>Thanks,</div><div><br></div><div>Rick Graves</div><div><br></div></div></font></div></div></body></html>