<html><body name="Mail Message Editor"><br>On Jun 14, 2008, at 8:08:47 AM, "Gerald I. Evenden" <geraldi.evenden@gmail.com> wrote:<br><blockquote style="padding-left: 5px; margin-left: 5px; border-left-width: 2px; border-left-style: solid; border-left-color: blue; color: blue; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: -webkit-monospace; font-size: 11px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; ">This is the place where we will apparently never agree. I would never use<span class="Apple-converted-space"> </span><br>small scale maps for distance/azimuth measurements and anyone who does is ill<span class="Apple-converted-space"> </span><br>advised.</span></blockquote>
<div>You know, Mr. Evenden, you are the one who touted the superiority of equal-area maps for such purposes (quoting from your previous e-mail):</div><div><br></div><div><span class="Apple-style-span" style="font-family: -webkit-monospace; font-size: 11px; ">>Extended geographic range usage of any conformal projection is a contentious <br>>issue as any resultant grid system has sufficiently large scale errors as to</span></div><div><span class="Apple-style-span" style="font-family: -webkit-monospace; font-size: 11px; ">>make the Cartesian usage of the grid very questionable.<br>>Your comment:</span></div><div><span class="Apple-style-span" style="font-family: -webkit-monospace; font-size: 11px; ">>>This is true of any projection. It is true that conformal projections carry</span></div><div><span class="Apple-style-span" style="font-family: -webkit-monospace; font-size: 11px; ">>>an inevitable disproportion of areas, but that's not related to scale error.<br>><br>>My sentense had nothing to do with area and by Cartesian usage I was denoting <br>>measuring distances, azumuths, etc. from the Cartesian data and it certainly <br>>seems that scale error greatly affects these measurements.<br></span></div><div><br></div><div>You're not arguing with me. I did not bring up using maps for arbitrary distance/azimuth measurements. You did, and you did so in order to prove the superiority of equal-area projections over conformal projections for small-scale usage. So now you are arguing with yourself. This is a matter of public record. So is the rest of your weaseling over the course of this discussion.</div><div><br></div><div>As far as your tirade below goes, I dare you to find anyone who thinks we should use maps when something else is better. I dare you to find someone who thinks most thematic mapping should be on anything other than equal-area maps. Those are straw men. Meanwhile, because you apparently can't imagine any use for small-scale maps that is not tied to area mensuration or estimation, you call for the elimination of conformal maps. You might ponder that it's dogma and your own limited imagination that lead you to such conclusions, not logic, and not real-world needs.</div><div><br></div><div>Regards,<br></div><div>-- daan Strebe</div><div><br></div><br><blockquote style="padding-left: 5px; margin-left: 5px; border-left-width: 2px; border-left-style: solid; border-left-color: blue; color: blue; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: -webkit-monospace; font-size: 11px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; ">I feel it is fair to say most small scale map usage is in the realm<span class="Apple-converted-space"> </span><br>of thematic mapping and and in such usage I feel that the principal factor of<span class="Apple-converted-space"> </span><br>concern is the sense of extent of a feature and its *area* of scope. A kind<span class="Apple-converted-space"> </span><br>of "my area is bigger than yours" attitude.<br><br>The best example of worst case usage of a conformal map is the classic<span class="Apple-converted-space"> </span><br>Mercator map of the world. One of its few practical uses is to demonstrate<span class="Apple-converted-space"> </span><br>the foible of measuring with this map and the rhumb line (loxodrome) and its<span class="Apple-converted-space"> </span><br>relation to the prefered measurement of a great circle or geodesic. It is<span class="Apple-converted-space"> </span><br>even rediculous to call it a map of the world when it can't even show the<span class="Apple-converted-space"> </span><br>poles due to the ultimate distortion of a singularity.<br><br>Lastly, I can put a dime on an equal-area map and the area that the dime<span class="Apple-converted-space"> </span><br>covers---in terms of real acreage on the ground---is the same anywhere on the<span class="Apple-converted-space"> </span><br>map, If I am looking at comparative areal extents of oil fields I have a<span class="Apple-converted-space"> </span><br>reliable method of comparison with the equal-area map. As for actual<span class="Apple-converted-space"> </span><br>measurements I can use a planimeter on the map and get a direct error-free<span class="Apple-converted-space"> </span><br>measurement.<br><br>If I were making a map of the areal extent of oil reserves in the Gulf of<span class="Apple-converted-space"> </span><br>Mexico I would definitely use an equal area map. This is the *only* class of<span class="Apple-converted-space"> </span><br>projection that properly displays the intent of the map and I can drop a dime<span class="Apple-converted-space"> </span><br>anywhere on the map and know that it covers the same number of square meters.<br><br>Lastly, I cannot think of a practical use of a conformal map of the Gulf<span class="Apple-converted-space"> </span><br>because all practical problems of distance/azimuth determination are micro<span class="Apple-converted-space"> </span><br>computer (or possibly shirt pocket calculator) functions with accuracy far<span class="Apple-converted-space"> </span><br>exceeding any scale layed on a map---and I do not mean using a cartographic<span class="Apple-converted-space"> </span><br>projection as an intermediate step unless it is to get data into the proper<span class="Apple-converted-space"> </span><br>units.<br><br>In fact, lets abolish conformal mapping altogether after we make sure all<span class="Apple-converted-space"> </span><br>coordinates of interest are stored as either geographic or geocentric x-y-z.<br>No more UTM, bastardized UTM, state/national plane coordinate system with wild<span class="Apple-converted-space"> </span><br>a wooly projections. Ahhh! Utopia! Unfortunately, when pigs fly.<br><br>> Regards,<br>> -- daan Strebe<br><br>--<span class="Apple-converted-space"> </span><br>The whole religious complexion of the modern world is due<br>to the absence from Jerusalem of a lunatic asylum.<br>-- Havelock Ellis (1859-1939) British psychologist<br></span></blockquote><br><div><br></div><div class="aol_ad_footer" id="u81CA46781F8F4F77B5E7A556FA1073F4"><FONT style="color: black; font: normal 10pt ARIAL, SAN-SERIF;"><HR style="MARGIN-TOP: 10px"><A title="http://toolbar.aol.com/moviefone/download.html?ncid=aolcmp00050000000011" href="http://toolbar.aol.com/moviefone/download.html?ncid=aolcmp00050000000011" target="_blank">Get the Moviefone Toolbar</A>. Showtimes, theaters, movie news, & more!</FONT></div></body></html>