What “large scale” means

Large scale means a detailed base, at scales such as 1:500 or 1:200, showing kerbs, structures, slopes and small changes in relief. The scale and the accuracy are set by the study, and the survey is planned from them. At Kriaritsi in Halkidiki, for example, we delivered a 1:200 topographic base for 13 square kilometres.

The methods

Control network and ground control points with GNSS: connected to HEPOS (the Greek GNSS reference network) and, for the main network of a large project, with static observations and least-squares adjustment
Total stations and precise levelling: Leica TS11/TS06 and the Leica DNA03 digital level, for stream beds, bridges, structures and points that need precise heights
Drone photogrammetry: Matrice 400 with Zenmuse P1 and Matrice 4E, for orthophoto maps and terrain models over large areas
Drone LiDAR: Zenmuse L2, when the study needs the ground under the vegetation
Bathymetry: when the study continues under water

Hydraulic studies

A hydraulic study needs a continuous, accurate relief of the bed, the banks and the structures. On the Gallikos river we delivered an orthophoto map and a terrain model for 33 kilometres of river bed, with an accuracy of about 3 centimetres. Where there is dense vegetation we fly LiDAR, as on the Agrafa stream, where the terrain model became the base for the hydraulic study of a stream demarcation. See the Agrafa stream project.

Roads

For a road study we survey a strip along the axis, with the carriageway, kerbs, structures, junctions and property boundaries where needed. On the road network of Central Macedonia we recorded about 500 kilometres of roads, combining drones, GNSS and 360° video from a vehicle.

Port works

Port and jetty studies need the land and the seabed or lakebed together. For the jetty at Psarades on Lake Prespa we combined a ground survey of the shore, drone photogrammetry and bathymetry, so that the designer had a single base.

Urban planning studies

In settlements we survey streets, buildings, property boundaries and relief, with an orthophoto map for the planning work. The terrain model in the Agrafa, for example, was produced within a Local Urban Plan.

Accuracy and checks

Over large areas, with RTK and ground control points, drone photogrammetry typically reaches an accuracy of 2 to 5 centimetres. Every survey is checked against independent check points that were not used in the solution, and the accuracy is stated in the technical report. Where the contract requires it, the work follows the specifications of P.D. 696/74 (Greek surveying specifications).

Deliverables

Digital terrain model and digital surface model (DTM/DSM)
Contour lines, cross sections and long sections
Orthophoto map in GeoTIFF/ECW
Topographic drawing in DWG/DXF, in GGRS87 (ΕΓΣΑ87), the national coordinate system of Greece
Point cloud in LAS/LAZ, where LiDAR is used
Technical report with the network, point coordinates and the accuracy check

What you need / steps

The study area, as KML, DXF or a sketch
The scale, accuracy and specifications required by the study
The deliverables and file formats the designer needs
Planning of the method and the flights; we obtain flight approvals where they are required
Survey, processing, checks and delivery

Send us the area and the specifications of your study, and we will propose the method that gives the accuracy you need.

Large-scale surveys for engineering studies: hydraulics, roads, ports, urban planning