Hydrographic surveys are defined by the Hydrographic Society of America as: "those surveys conducted to determine the configuration of the bottom of water bodies and to identify and locate all features, natural and man-made, that may affect navigation.  Nautical charts are compilations of data from numerous sources, principally hydrographic surveys, designed specifically to meet the requirements of marine navigation.  The scope of these standards includes the coastal waters of the U.S. and its territories."  At Geo-Marine Technology, we produce charts from data collected by survey companies. We pride ourselves in not only exceeding standards of the Hydrographic Society of America, we feel we are more precise than the stringent standards of the International Hydrographic Society

Key Benefits

• High degree of precision - every sounding is individually corrected for metadata (tides, sound velocity etc.)
• Contours are generated by using TIN modeling, not the imprecise "gridding" methods that are so commonly practiced.
• Contours are AutoCAD polylines with appropriate elevations assigned to each contour.
• DTMs and ArcView formats supported as deliverables
• 3-D visualizations such as wire mesh diagrams, and colored surface displays can be easily generated for a nominal charge.
• When available, we integrate side scan sonar information and seafloor reflective impedance information.

Capabilities

We can take in nearly any kind of data, from simple analog strip charts to high volume digital datasets as long as X, Y, and Z components are decipherable.  Whenever possible, we correlate side scan sonar features to provide accurate modeling between survey track lines.  Our in-house hydrographic reduction software individually calculates and corrects each sounding from available metadata. 

Independent Sounding Reduction

Using in-house programs that independently calculate values for corrections for each sounding, we can produce bathymetric information with a high degree of accuracy.  These programs include tide correction application, sound velocity correction (from SVP profiles with any number of data points in each profile), vessel squat corrections for variable vessel speeds, and draft corrections

TIN Modeling 

TIN modeling (triangular irregular networks) calculates contour locations with a much higher degree of precision than the popular gridding techniques used so broadly.  Where gridding can handle large numbers of "dirty" data points and come up with approximations at binned locations, TIN techniques require a "clean" dataset with little or no invalid values (we take the time to correct spikes rather than statistically average bins).  Because of the complexity of the technique and the hand-correction that must be employed to create a "clean" dataset, the TIN technique is not widely used today.  It just takes too much work which cuts into profits.  We feel that the added benefit of variable spatial resolution provided by TIN techniques is extremely important to dynamic seafloor modeling, especially in areas of high topographic variability. 

3D Contouring

We produce 3D AutoCAD polyline contours that can be loaded and displayed in a broad variety of platforms.  AutoCAD is an industry standard and nearly all graphics programs and geologic/hydrographic analysis programs allow the import of AutoCAD 3D polylines as either DXF or DWG file formats.

Easy integration of side scan sonar data   

Our sonar mapping programs are designed to create outputs that import directly into AutoCAD.  Where swathe bathymetry data is not available, this enables us to model the seafloor topography between by using either sonar mosaics or interpreted features between survey track lines.

2D High Density Sampling

We can produce SEG-Y files that can be interpreted in workstations.  We can output "clean" soundings at the ping rate (sometimes several soundings per lateral foot).  At this time we are the only company we know of that has this highly precise technology.