Data Processing, QA/QC, GIS Integration, and Map Production

Data Processing, QA/QC, GIS Integration, and Map Production

This lesson brings together every dataset your team has collected in the field—drone imagery, ground control points (GCPs), GNSS observations, and total-station traverse measurements—and walks them through a structured processing pipeline that ends with a professional, print-quality map package. Each stage requires a documented quality-assurance and quality-control (QA/QC) check before you move to the next. Skipping or rushing QA/QC is the single most common cause of deliverables being rejected in professional practice.

Photogrammetric Processing and Orthomosaic Generation

Begin by importing your raw drone imagery and GCP coordinate file into your photogrammetric software (Agisoft Metashape or an equivalent program). The processing sequence follows a fixed order: image alignment, dense cloud generation, digital elevation model (DEM) creation, and finally orthomosaic export as a GeoTIFF.

After alignment, the software reports a root-mean-square (RMS) error for each GCP. The RMS value tells you how well the photogrammetric model matches your measured ground positions. Compare every GCP RMS against your project accuracy target. A common field rule is to flag any GCP residual that exceeds twice the target error; those points must be investigated before continuing. Causes include a misidentified target, a data-entry typo in the coordinate file, or a target that shifted between the time it was measured and when the flight occurred. Resolve the issue—do not simply delete the point without a written explanation in your project log.

Export the final orthomosaic and DEM as GeoTIFF files. Record the coordinate reference system (CRS), pixel resolution, and the RMS values for every GCP in your processing report. This documentation is your audit trail.

Traverse Adjustment and Coordinate Geometry

Your total-station traverse must be adjusted before any coordinates from it are used in the GIS. Use your traverse adjustment software or the provided spreadsheet template to apply a compass-rule (Bowditch) adjustment or least-squares adjustment, depending on project requirements. Verify that the angular misclosure and linear misclosure are within the tolerances specified for your project class of survey. Document the unadjusted misclosure, the adjustment method chosen, and the final adjusted coordinates. These records follow NSPS survey documentation guidelines and are required if your data is ever used in a legal or regulatory context.

GIS Integration in ArcGIS Pro

Open your ArcGIS Pro project and confirm that the project CRS matches the CRS used throughout field collection and photogrammetric processing. Import or georeference all datasets into this single CRS:

• Adjusted traverse and GNSS point coordinates
• Orthomosaic GeoTIFF
• DEM GeoTIFF
• Any existing base data (parcel lines, control monuments)

Digitize or import topographic breaklines along ridges, drains, and edges of pavement where the terrain changes slope sharply. Generate contours at an interval appropriate to your site relief and accuracy class. Digitize site features—buildings, fences, utilities, vegetation boundaries—as separate feature classes with correctly typed geometry (point, line, or polygon).

Run the ArcGIS Pro Topology tool after all feature classes are populated. Set topology rules appropriate to your data (for example, contours must not cross; parcel polygons must not overlap). Resolve every topology error before proceeding—a deliverable with unresolved spatial errors fails QA/QC.

Populate all attribute tables using the project data dictionary so that every feature has a complete, consistent set of attributes. Attach FGDC-compliant metadata to each layer and to the project as a whole, recording the data source, date of collection, horizontal datum, vertical datum, accuracy, and the name of the person responsible.

Map Layout Design and Export

Produce three map layouts in ArcGIS Pro:

1. Topographic map — contours at the project interval, spot elevations at key locations, and all surveyed features.

2. Orthomosaic map — georeferenced orthomosaic as the base, with GCP locations labeled by point ID and their reported RMS values in a callout table.

3. Thematic analysis map — a site-specific GIS analysis result such as slope classification (derived from the DEM using Spatial Analyst), cut-and-fill zones, or a drainage area delineation.

Every layout must contain these standard cartographic elements: title, scale bar with stated units, north arrow, legend, datum and projection note, author name, and date of production. Export each layout at a resolution suitable for print (minimum 300 dpi for raster content). Save all exported files to the project external hard drive and verify the backup before closing the software session.

QA/QC Mindset and Data Security

QA/QC is not a final step—it is woven into every stage. Keep a running QA/QC log using the project checklist. If a check fails, stop, document the problem, correct it, and re-run the check. Never overwrite raw data files; always work on copies and maintain the originals in a separate folder clearly labeled as raw data. Before leaving your workstation at the end of a session, back up all project files to the external hard drive. Data loss from an unsaved session or a failed drive is a preventable project failure.

From a physical safety standpoint, long processing sessions on a workstation require ergonomic awareness: position your monitor at eye level, take brief breaks every hour, and keep cables and drives secured so they do not create trip hazards in a shared lab space.