Pennsylvania Spatial Data Access

Abstract:

A spot elevation is an elevation measurement taken at a single location. It shows the height of ground above Mean Sea Level (M.S.L.). This layer consists of spot elevations for DVRPC's 9-county region and was generated from an aerial topographic survey in 2005.The Delaware Valley Regional Planning Commission's (DVRPC) 9-county region is made up of the following: Bucks, Chester, Delaware, Montgomery, and Philadelphia counties in Pennsylvania; and Burlington, Camden, Gloucester, and Mercer counties in New Jersey.

Purpose:

To be used for planning purposes.

Currentness_Reference:

ground condition

Use_Constraints:

The Delaware Valley Regional Planning Commission (DVRPC) excludes any and all implied warranties of merchantability and fitness. No guarantees are expressed or implied as to the use or application of the digital information supplied. DVRPC assumes no responsibility to maintain them in any manner or form. DVRPC will not be liable for any direct, indirect, special, incidental, or consequential damages arising out of the use or inability to use the material supplied, or arising out of any inaccuracy or defect in the digital information supplied. Recipients of DVRPC digital files are not entitled to any file revisions, updates, corrections, or new releases. Recipients of DVRPC digital files are expressly prohibited from copying or releasing these files to any other individuals or agencies, under any circumstances. Recipients of DVRPC digital files are expressly prohibited from displaying for view or making these files available for download from the Internet or World Wide Web, under any circumstances. Recipients of DVRPC digital files will credit DVRPC as the source of the data when producing maps, publications, reports, or other documents that utilize DVRPC files.

Address:

124 Gaither Drive

Address:

Suite 100

Data_Set_Credit:

BAE Systems

Attribute_Accuracy_Report:

The accuracy of the ground control is confirmed by the evaluation of the results of the analytical bundle adjustment. The residuals of the final adjustment ensured compliance with NSSDA standards. The Pre Adjustment Gross Error Detection Statistical Test (Data Snooping, with a confidence level of 99.9%) has been applied to all observations included in the aerial triangulations. To detect small gross errors, during Adjustment Robust Estimators were used with the same confidence level and a power of the test of 1-beta=0.2. Systematic errors were eliminated through self calibration and through Additional Parameters. Their numerical stability, statistical significance, internal and external reliability were checked using Student-t test with the same confidence level and Variance/Co-variance analysis. Finally, the arrived variance factor was submitted to a Chi-square test against the pre-adjustment variance factor using a confidence level 99.9%. Evaluation of the DEM includes checking the terrain data for spikes and wells, omissions, and other anomalies that do not meet the project accuracy requirements. The horizontal and vertical accuracy has been tested by comparing the coordinates of well-defined points in the dataset with coordinates of the same points from an independent source of higher accuracy.

Logical_Consistency_Report:

All files are inspected by the Production Manager to ensure that they conform to the specified file naming conventions, all files load in their correct geographic position, all files conform to the project specifications. The data has been checked for duplicate features, correct edge matching, overshoots, undershoots, offsets, overall cartographic appearance.

Completeness_Report:

The data has been checked to ensure that the boundary and the content has been covered in its entirety.

Horizontal_Positional_Accuracy_Report:

The horizontal accuracy standard follows the NSSDA-1998 standard. The maximum permissible RMSE for 95% of the horizontal check points for the mapping product is 5 feet or better.

Vertical_Positional_Accuracy_Report:

The DEM data meets the required vertical accuracy necessary to ensure that the contours meet NMAS for 1"=200', 5' CI mapping.

Source_Contribution:

To be utilized in the analytical aerotriangulation process. All horizontal and vertical control was prepared under the supervision of licensed Professional Land Surveyors.

Source_Contribution:

Color Aerial photography to be used in the creation of digital orthophotos.

Process_Description:

Horizontal and Vertical control points were acquired utilizing GPS collection techniques. All control was prepared under the supervision of licensed Professional Land Surveyors.

Process_Description:

Color aerial imagery captured with the Leica ADS40 digital camera system and PAV30 gyro stabilized mount. The photography was captured at a flying height of 9,500' utilizing GPS and IMU technology and conforms to ASPRS's Draft Aerial Photography Standards (1995).

Process_Description:

The airborne GPS data were processed and integrated with the IMU. The results were imported into the ISTAR system for use in the aerotriangulation. The ADS40 imagery was downloaded onto the server and brought over to the UNIX based ISTAR system. The ground control was used in conjunction with the processed ABGPS results for the aerotriangulation. The properly formatted ISTAR results were used for subsequent processing.

Process_Description:

The procedure utilized for the development of the DTM/DEM consisted of experienced photogrammetric technicians manually collecting masspoints and breaklines at a sufficient density that will ensure accurate generation of five foot contours as stated in the project specifications. Existing "Contour Grade DEMs" were available from previous Chester County and City of Philadelphia projects. These DEMs were reviewed and updated as necessary to reflect the terrain conditions of the new 2005 imagery to insure that the resulting contours meet NMAS for 1"=200', 5' CI mapping.

Process_Description:

Five foot contours were generated from the DEM using 3D Analyst in ArcMap. The contours were re-projected to UTM, Zone 18, NAD83, meters. The contour values have a metric equivalent of the state plane, feet generated contours. Spot elevation labels were also converted to their metric equivalent.

Attribute_Definition:

Internal feature number.

Attribute_Definition_Source:

Esri

Attribute_Definition:

Feature geometry.

Attribute_Definition_Source:

ESRI

Entity_and_Attribute_Overview:

All features were captured in conformance with accepted photogrammetric mapping procedures.  This data set contains the following features:  breakline, digital_elevation_model_point, control_point, obscured_area, elevation_contour_line, spot_elevation_point.

Entity_and_Attribute_Detail_Citation:

Where applicable, all data conforms to the Proposal for 2005 Aerial Photography Project presented to the Delaware Valley Regional Planning Commission August 5, 2004.

Address:

190 N. Independence Mall West

Address:

8th Floor

Distribution_Liability:

Recipients of DVRPC digital files are expressly prohibited from copying or releasing these files to any other individuals or agencies, under any circumstances. Recipients of DVRPC digital files are expressly prohibited from displaying for view or making these files available for download from the Internet or World Wide Web, under any circumstances.

Address:

115 Land and Water building

Distribution_Liability:

The USER shall indemnify, save harmless, and, if requested, defend those parties involved with the development and distribution of this data, their officers, agents, and employees from and against any suits, claims, or actions for injury, death, or property damage arising out of the use of or any defect in the FILES or any accompanying documentation. Those parties involved with the development and distribution excluded any and all implied warranties, including warranties or merchantability and fitness for a particular purpose and makes no warranty or representation, either express or implied, with respect to the FILES or accompanying documentation, including its quality, performance, merchantability, or fitness for a particular purpose. The FILES and documentation are provided "as is" and the USER assumes the entire risk as to its quality and performance. Those parties involved with the development and distribution of this data will not be liable for any direct, indirect, special, incidental, or consequential damages arising out of the use or inability to use the FILES or any accompanying documentation.

Address:

Suite 100

Address:

124 Gaither Drive

DVRPC 2005 Spot Elevations