Historical aerial photograph analysis for areas with suspected ordnance

It is particularly useful where no reliable assessment of possible ordnance contamination is available before land development, planning, tendering, drilling or excavation. Older reports, unclear information from authorities, known finds nearby or previous military or war-related use may also prompt an assessment. A clearly defined investigation area and planned ground intervention are essential.

Depending on the task, sources may include historical maps, records, site histories, war-damage documents, previous clearance reports, known finds, information from authorities, current cadastral and geographical data, and existing project reports. The type and extent of research depend on the project area, available sources and required conclusions. Each significant source is documented with its provenance and spatial relevance.

The project boundary, interventions and existing information are checked first. This is followed by image and archive research, comparison of different dates, spatial transfer, assessment of findings, and the report and maps. The chronological sequence helps distinguish wartime features from later earthworks. Official enquiry procedures and private specialist analysis are coordinated for the project location; existing statements are considered with their complete annexes and respective scope.

Historical analysis assesses sources and suspected contamination; it is not a technical investigation of the present-day ground. It can delineate historical indications, document an absence of indications and justify further measures. Its conclusions nevertheless depend on image coverage, visibility, available sources and their applicability to the current project area. Where these foundations are insufficient, further assessment remains necessary.

If a suspicious object is actually discovered independently of the report, work is stopped. The object is left untouched and unchanged; the immediate area is vacated and, in Germany, the police are called on 110. Outside Germany, the local emergency procedure applies. Historical analysis does not replace reporting a find.

The report describes the reason for the assessment, investigation area, project context, sources used, historical site development, identified findings, spatial attribution, data gaps and specialist evaluation. Supplementary maps show project boundaries, findings, possible suspect areas and positional uncertainties. The conclusion explains which further research, technical survey or measure accompanying construction may be appropriate for the planned intervention.

Achievable accuracy depends on acquisition geometry, image scale, control points, terrain and the quality of historical maps. Findings are transferred to a current coordinate system using suitable references. Where an exact point location cannot be justified technically, an uncertainty area is shown. Subsequent technical assessment is then based on the defensible area rather than an apparently exact individual coordinate.

Useful information includes the project address, current site plan, cadastral parcel, construction-site or route boundary, planned intervention depths, construction phase, schedule, existing correspondence with authorities, previous reports, known finds and a brief description of the decision required. For drilling or foundations, point lists and target depths should be included.

Factors include the size and shape of the investigation area, the number and quality of available aerial photograph series, necessary archive and map research, historical complexity, present-day alterations, required report detail, data formats and schedule. Reliable costing therefore requires an unambiguous project polygon, planning status and required conclusions.