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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inconsistent results from DTEDFrame.interpElevationAt()","articleBody":"The method DTEDFrame.interpElevationAt() is producing unexpected values for the output elevation value.  As an example, using a sample DTED2 elevation file and point lat=-14.123 (index=3157.1995) and lon=-68.555 (index=1601.9989) the nearest 4 elevation posts in this dataset are:\r\n\r\nur = 1513\r\nul = 1522\r\nll = 1523\r\nlr = 1515\r\n\r\nManually calculating a bilinear interpolation shows that the output elevation should be very close to the lower-right elevation post which is 1515 meters, but the resulting value is near the upper-right post (i.e. 1513).  The code is not utilizing the lower elevation posts to generate the output interpolated value.","author":{"url":"https://github.com/carpenlc","@type":"Person","name":"carpenlc"},"datePublished":"2019-10-09T14:18:53.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/50/openmap/issues/50"}