Raw and modified raw continuous resistivity profile data collected in Northport Harbor on Long Island, New York on May 14, 2008

The continuous resistivity profile (CRP) system used on this cruise was an AGI SuperSting marine system described at the website: www.agiusa.com/marinesystem.shtml. Two different streamers were used for data collection - not simultaneously. One streamer was a 50-m streamer with an 11 electrode array with electrodes spaced 5 meters apart. The other streamer was a 15-m streamer with an 11 electrode array with electrodes spaced 1.5 meters apart. In both cases, the source electrodes are graphite, while the receiver electrodes are stainless steel. A dipole-dipole configuration was used for the data collection in which two fixed current electrodes are assigned with the measurement of voltage potential between electrode pairs in the remaining electrodes. The maximum depth below the water surface the streamer can reach is approximately ¼ the streamer length. So for the 50-m streamer, maximum depth is about 12.5 meters, while the 15 meter streamer can reach about 3.75 meters. Each line of data acquisition records several files. The two files necessary for processing are the *.stg and the *.gps file. The STG file contains the resistivity data, while the GPS file contains the navigation information. The navigation system used in concert with the CRP system is a Lowrance LMS-480M with an LGC-2000 GPS antenna and a 200 kHz fathometer transducer. The transducer also contains a temperature sensor. Lowrance indicates the speed of sound used by the system is 4800 feet/second. Both the temperature and depth information are recorded in the logged GPS file. The CRP system images the subsurface electrical properties of an estuarine, riverine or lacustrine environment. Resistivity differences can be attributed to subsurface geology (conductive vs less conductive layers) and hydrogeologic conditions with fresh water exhibiting high resistivity and saline conditions showing low resistivity.

On this day of data collection, both the 15-m streamer and the 50-m streamer were used. Also, this day a different Sting box was used for data acquisition - one sent from AGI. The data were transferred from the logging computer via AGISSAdmin software version 1.3.2.165. These files were then transferred via a thumb drive to the processing computer. The files included in this publication are the *.crs, *.cmd, *.gps, and *.stg. The two files essential for processing are the GPS and STG files. The GPS file contains the navigation, and in the case of the Lowarance system also includes water depth and water temperature. The STG file contains the resistivity measurements from each of the electrodes. The CRS file contains the contact resistance readings. The CMD file contains the parameters for data collection. These last two files aren't necessary for data processing, but can be useful in terms of troubleshooting. The 15-m streamer files include L33F1, L33F2, L34F1, L35F1, L36F1, L37F1 and L38F1. No L39F1 exists. The remainding lines (L40F1, L41F1, L42F1, L43F1, L44F1, L45F1, L46F1, L47F1, L48F1, L49F1, L50F1, and L51F1) were collected with the 50-m streamer. The collection of the data included the proper scaling for the correct electrode spacing. Additionally, the first electrode offset was entered appropriately (-2 for the 15-m streamer and -15 for the 50-m streamer) so no additional GPS offset will be necessary in the post-processing. This process step and all subsequent process steps were performed by the same person - VeeAnn A. Cross.

Viewing the previously processed navigation based on the GPS files indicates a large navigation gap in L38F1. In order to process this file, the file had to be split into two parts. VI (v. 7.2) under CYGWIN (v. 1.5.1) was used to split the initial files saving the results in L38F1_part1 and L38F1_part2.

Edits to the metadata were made to fix any errors that MP v 2.9.36 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Attempted to modify http to https where appropriate. Reordered the links in the identification section to have a landing page link as the first link. Updated the link to the field activity. Moved the minimal source information provided to make it the first process step. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent.

Added keywords section with USGS persistent identifier as theme keyword.