19 Professional Land Surveyors of Oregon | www.plso.org Featured Article As can be seen in the above table and figures, the 2022 datum will result in elevations that are around 3.5 feet lower than NAVD88. In places such as Medford, Newport, Salem, and Ontario, NAPGD2022 elevations will fall within a few hundredths of the published NGVD29 benchmark elevation. An area of south-central Oregon between Burns, Lakeview, and Chemult will have an elevation one foot higher than NGVD29. The northwest coast and spots along the Columbia River will drop a few tenths of a foot lower than NGVD29. NGS has stated on their FAQ page (link referenced in first paragraph) that they will not be providing tools to transform between NGVD29 and NAPGD2022 directly. Instead, they will be providing tools that transform NAVD88 to NAPGD2022. For those who need to transform from NGVD29 to NAPGD2022, they recommend intermediate transformations. This means you will need to use VERTCON to go from NGVD29 to NAVD88, and a new tool to go from NAVD88 to NAPGD2022. Of course, if the benchmark still exists and is undisturbed, the best way to get the difference in datums is to directly observe in the new datum and reference frame. Andrew Plett is a PLSO & ACSM scholarship recipient, and 2006 Oregon Institute of Technology graduate. He has worked in Oregon and Washington since graduation, and currently works with S&F Land Services at their Vancouver, Washington office. Figure 2: The tabular data visualized as a contour map Ronnie Jacko [email protected] | 503-445-2234 continued
RkJQdWJsaXNoZXIy MTY1NDIzOQ==