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2 <br />SMALL =ACCURATE <br />How do you attain an <br />accurate wetlands map? <br />Think small. What is the <br />smallest. area that may be <br />mapped. through air photo <br />interpretation? This question <br />is at the heart of production of <br />accurate wetlands maps. <br />Mapping scientists refer to the <br />smallest consistently <br />identifiable area as the <br />"minimum mapping unit". <br />jmai{ 1."ret=ands ure i' vet <br />accurately mapped when <br />located in non-forested areas <br />and when color infrared aerial <br />photography is used. Color <br />infrared can distinguish moist <br />soil very wel( allowing <br />wetlands to be identified when <br />there is no standing water. <br />Wetlands in the agricultural <br />areas of Minnesota, for <br />example may be consistently <br />mapped to a scale of 1/10th to <br />1 /4 acre using 1:40,000 scale <br />National Aerial Photography <br />Program color infrared aerial <br />photography. Often smaller <br />areas are mappable <br />depending how distinctly they <br />contrast with their <br />surroundings <br />When wetlands are covered <br />by trees accurate mapping is <br />more challenging. The forest <br />canopy often obscures smaller <br />wetlands. However, forested <br />wetlands may be inventoried <br />with a higher degree of <br />accuracy when aerial <br />photography is intensively <br />checked in the field and cross <br />referenced with other existing <br />f I~UppGd infCl ma~. ~ivi i ar id <br />aerial photos. <br />However, !ow aftit~,~de aerial <br />photos will often yield greater <br />detail than NAPP <br />photography. Wetlands which <br />are not obscured by trees may <br />have, virtually, no minimum <br />mapping unit. However, low <br />altitude aerial photography <br />requires much more time and <br />higher levels of skill in <br />interpretation. The suitability. <br />for interpretation also varies <br />extensively. Low altitude <br />photos are often not color <br />infrared. Photography may <br />not have been taken at the <br />right time of the year or may <br />not completely cover the <br />project area.. <br />Air photo interpretation will <br />provide you with more <br />accurate information than that <br />currently available from <br />existing government sources. <br />These detailed maps will help <br />you make more of your <br />decisions in the office. You <br />will be able to reduce the <br />number of time consuming <br />and costly field investigations <br />needed t`J un$wer many of <br />your wetlands questions. <br />Wetlands Data <br />A Division of EnviroData <br />5831 Cedar lake Road <br />Minneapolis, MN 55416 <br />Edward Roberts <br />Grass Lake WMO <br />4600 N. Victoria St. <br />Shoreview, MN 55126 <br />BUUC RATE <br />U.S. POSTAGE <br />PAID <br />MINNEAPOLIS, MN <br />PERMfr N0.26164 <br />11~:L'. f.~fi~~'11Z tii:l: is i:s:it<: i:l:li:: =::.lti 11:1[fE~~til~Sfllii~k:fil~}Ili~~~:lt}Ili!!:!II~ <br />V~/ETLANDS DATA <br />