This project involved a single beam / side scan survey of approximately 8 miles of the Harlem River from the East River to the Hudson River. The high frequency (200Khz =/- 15%) single beam line spacing measured approximately 50 ft. At the time of the survey the Federal Channel limits were unknown, so the survey extended from bank to bank as water depth safely allowed. McKim & Creed used side scan to support the bathymetry and to identify the areas of interest between the single beam lines. A side scan survey with 100% coverage of the bounding federal coordinates provided by the Corps of Engineers was also performed.
All sounding data was referenced to the plane of Mean Lower Low Water (MLLW) of the current epoch. Because of the tidal range and geographical dynamics of this area, the reference plane of MLLW varied throughout the channel. VDatum was used obtain these values using Vdatum2xyz within HYPACK.
Soundings were plotted to the nearest 0.1 foot with the decimal point indicating the position of the sounding. Single beam soundings were sorted to 10-ft radii with channel priority. Mapped sounding data was supported with raster and project depth contours using the single beam dataset. A total of 116 targets were identified and mapped.
The final mapping was performed to adhere to A/E/C CADD standards using HYPACK, Bentley Inroads V8i and Microstation V8i. Existing digital orthos/aerial mapping supplied by the government was incorporated into the final .DGN files. Other deliverables included copies of field notes and log books, single beam and side scan survey reports, and a side scan target report.