This Request for Proposal (the “RFP”) is an invitation by The Niagara Peninsula Conservation Authority (“NPCA”) to prospective proponents to submit proposals to update the existing 1-meter contour supporting Digital Terrain Model (DTM) for the Niagara Watershed (Watershed) that corresponds to its jurisdiction as further described in ‘Appendix D - The RFP Particulars’
 

The update is intended to bring the existing DTM into currency with the NPCA’s 2020 orthoimagery using the associated stereo models and geo-positioning information available for this source aerial photography. This section outlines the assignment and the terms and conditions that will govern the assignment

Background

The Niagara Peninsula Conservation Authority originally partnered in the 2002 Greater Toronto and Area Orthophotography and Digital Elevation Model (DEM) Project to acquire digital aerial imagery and elevation information capable of being ‘used for pre-engineering survey and design, the production of municipal planimetric mapping and detailed topographic mapping at a minimum scale of 1:2000 with a contour interval of no less than one meter (1.0 m).’

The elevation data delivered to meet these guidelines resulted in a DTM with a minimum 0.5 meter horizontal and vertical accuracy It was photogrammetrically derived to meet the accuracy requirements of the former Flood Damage Reduction Program (FDRP) specifications for 1m contours. As a 1-meter contour supporting DTM, it means that 90% of all derivative 1-meter contours and elevations of points interpolated from its derivative surface and 1-meter contours are accurate to within one half the contour interval. This product has served the NPCA extremely well by enabling its capital floodplain mapping program, shoreline flood and erosion hazard mapping updates, riverine erosion hazard feature and associated valley land identification, development of a water budgeting spatial framework, and the compilation of a large-scale surface water inventory (hydrologic mapping). As a critical information asset, this DTM information was updated by the Authority through a subsequent 2010 orthoimagery acquisition that occurred across the NPCA watershed with a change detection emphasis on hydrology features beyond that typically required for rectification purposes of its source imagery.

The scope of previous change detection efforts to the DTM generally addresses typical temporal updates to the modeled bare ground surface related to ongoing development activities within the watershed, and ortho rectification needs. Edge features for roads are added and the elevation grades are adjusted in newly urbanized areas to reflect development in the model; however, more change detection focus in rural areas across the full spectrum of breakline types was emphasized as well. The 2010 effort addressed hydrology features that had been largely overlooked from previous partial updates to the watershed-wide dataset from various sources and in between projects. The breaks that define surface waters and their associated morphology were updated where they had come to exceed the minimum accuracies of typical large-scale mapping specifications which are directly related to the source imagery and elevation acquisition guidelines for these types of projects. This has better enabled the updated DTMs for water resource management applications, such as the development of derivatives like spatially accurate large-scale surface water inventories, or the geometry characterizing channels and floodplains for hydraulic modeling support.

In 2020, the NPCA partnered again with a broad list of public agencies to participate in the SWOOP 2020 Orthophotography acquisition project through Land Information Ontario, a division of the Ministry of Natural Resources and Forestry. The specifications that were used for this project demanded 16 cm pixel resolution with an accuracy of 50 cm (horizontal and vertical) to obtain highly accurate information that could be used for a variety of purposes. It used a digital sensor and included as deliverables for the entire Watershed;

• flight indices and reports,
• the raw images,
• aerial triangulation (AT) data,
• block stereo models,
• digital orthophotos (12 cm GSD).

The intent behind acquiring the additional photogrammetric products through this acquisition project, not unlike 2010, was so that participants could use this data in their own softcopy and stereo environments or provide them on to vendors for additional works such as planimetric feature collection, detailed DTM compilation, or pixel correlated Digital Surface Model (DSM) extraction.

It is this SWOOP 2020 based information (stereo models) that the NPCA proposes to use to update the existing 2010 1m contour supporting DTMs for its entire Watershed using the traditional photogrammetric compilation method of stereo digitizing. As already stated, these products have been used in the past to provide similar digital terrain data updates that support detailed topographic mapping at a minimum scale of 1:2,000 with a contour interval of no less than 1-meter. Several derivatives such as the 1m contours, watershed-wide 2 and 3D mass point and breakline datasets, and interpreted surfaces are desired as well.