FEMA FIRM map fraud
The FIRM maps don't reference what basis was used for their elevations. To use the benchmarks they would have had to identify the NGS benchmarks somehow on the imagery they used to develop the Flood areas. I'm fairly certain precise photogrammetry wasn't used. What bothers me is the flood boundaries don't follow contour lines either. There appears to be to be no logic to how somebody created those boundaries. The FIRM maps do state the accuracy is to their standards, which are 24.5 cm (0.8 Feet) to 147 cm (4.8 Feet). NGS doesn't state what their accuracy standards are on the Data Sheets. Maybe its somewhere else. When I get an OPUS report back it tells me what the 1-sigma RMS values are. I'm ignorant as to exactly how they are creating Ortho Heights using GEOID18, but the geiod information has been pretty reliable to me in the past.
Again my argument is Government Agencies should not be interpolating FEMA FIRM map elevations to 0.1 foot. I'm not even sure it should be 1.0 feet.
Fraud is a serious accusation. You raise some points worth discussing, but nothing you have described sounds like fraud to me.
I personally wouldn’t use OPUS to do a flood certificate. It might be a good check.
I believe that for most areas the Gov utilized a mixture of Quad maps and Aerial data. In PLSS areas any way.
FIRM maps are better than nothing. That sums it up completely.
I own property in a city that has a new FIRM map dated 2010. That is a fallacy. The Government completed their analysis in 2005. They spent five years going through various reviews, including local public meetings, before publishing in 2010. We had a tremendous river flood occur in 2007 that exceeded the flood boundary on the old FIRM map by two feet in those parts of the city based on river flooding. The part primarily based on a creek was as much as six feet lower than the old flood boundary. It was too late to include the 2007 data.
The lots that I own were shown to be about one-third in the flood plain on the old map. The 2010 map shows them to be out completely. Last year we had a flood event. Every inch of those lots was under water of varying depths. It will be about 2030 or later before an updated FIRM may be published.
Several other cities had similar and worse flooding in 2007. Six and eight feet higher than the magic old FIRM number, in fact. We had been scheduled to survey a property with a house that had a LOMA showing it to be out of the flood plain. That job was canceled as the house had water about four feet deep above first floor level. We drove by a couple of weeks later to see numerous houses in that part of town abandoned.