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Topographical (land) Surveys
and related services

 

Our Surveyors work to RICS Guidelines using Leica Total Stations and have experience of surveying a wide variety of subjects including Schools, Sports facilities, Recreation grounds, Residential gardens, Woodland, Highways, Equestrian facilities, Farmland and Supermarket car parks.

UAV Piloting is undertaken with full CAA PfCO approval & with training to Level 4 Award for Commercial Drone Pilots, working to CAA regulations in accordance with our certified Operations Manual.

From our topographical surveys we can produce TIN surface models, contour models and site sections all based on the ground spot levels measured on site.

Using GNSS RTK, we routinely orientate our surveys to Ordnance Survey grid and Newlyn datum. We can also orientate existing 3rd party surveys and measure the position of 3rd party survey markers such as UAV ground markers

Levels-only surveys is a Value Management consideration. A full topographical survey might not be necessary. For a preliminary Environmental terrain study, for example, it may be adequate to simply acquire a grid of spot levels (using GNSS RTK or UAV) and then overlay them to an existing map or plan, such as a licenced OS map extract or a Title Plan.

Topographical Surveys

 

Experience

Our Surveyors have experience of surveying a wide variety of subjects including Schools, Sports facilities, Recreation grounds, Residential gardens, Woodland, Highways, Equestrian facilities, Farmland and Supermarket car parks.

Procedural Approach

Surveys have ranged in size from residential plots to dozens of acres, following a meticulous, procedural approach using certified Leica Total Station equipment and following RICS guidelines.

Remote Measurement

Using our EDM equipment we can generally acquire measurements which cannot be reached from the ground or where direct access is not practical or permissable such as neighbouring property ridge and eaves heights and other detail up to 1km range.

Presentation

We expertly draft the final survey plan in traditional 2D, accurately using CAD, with quality control procedures to ensure consistency and clarity of presentation. Plans are presented to standard ISO sheet sizes and to appropriate scales between 1:50 and 1:2500, as applicable.

Discretion

Your survey will be undertaken by a qualified, experienced surveyor, working to the RICS code of ethics. We are very discrete & experienced with fielding questions from passers-by about developments. We are courteous at all times. We aim to minimise any disruption to the ongoing operational activies on site. We have experience working on secure sites such as care homes and schools. DBS (Enhanced) reports for our surveyors can be provided if legitimately required.

Pricing

We offer free fixed price quotations. We assume competive tender and give our best price based on our estimate of time & costs. Every survey is different, with a varying timescale (dependent on site size, logistics & detail) & travel costs.

However, as a ballpark, our prices start as low as £500+VAT for a small residential plot.

Sustainable

We aim to undertake our quotations remotely to avoid unnecessary travel, in keeping with our Environmental Policy. We use Google Maps or BING. These may not provide the full picture. So we are grateful if the client can provide photographs & a rough outline to show the extent of the survey area on plan. We also supply the finished plan electronically, in DWG and PDF formats. Though,we can provide paper copies at your discretion and convenience (see printing fee structure).

Orientation

We accurately orientate our land surveys to Ordnance Survey grid and to Newlyn (ODN) datum using GNSS RTK. Though we can use client orientation or datum, if required.

UAV / Drone Surveys

 

CAA Certified

UAV Piloting is undertaken with full CAA PfCO approval & with training to Level 4 Award for Commercial Drone Pilots, working to CAA regulations in accordance with our certified Operations Manual.

Highly Efficient

Surveys have ranged in size from residential plots to dozens of acres.

Photogrammetry

The UAV process involves the capture of hundreds of overlapping photographs. The commercial registration software is able to stitch together and to calculate the height of any point in the images. This is similar to the process used by your eyes for depth perception or binocular vision and is highly accurate.

Terrain Modelling

We can generate terrain models such as meshes, TINs and contour models. These can be integrated with existing map data.

Detail Vectorization

Working from orthographic or sectional projections, we transpose/vectorise survey detail too - such as buildings, fences, roads, etc - to the final survey plan in traditional 2D, accurately using CAD, with quality control procedures to ensure consistency and clarity of presentation. Plans are presented to standard ISO sheet sizes and to appropriate scales between 1:50 and 1:2500, as applicable.

Orientation

We accurately orientate our land surveys to Ordnance Survey grid and to Newlyn (ODN) datum using GNSS RTK. Though we can use client orientation or datum, if required.

Photography

Detailed photographic images can be captured, for instance a building roof for maintenance purposes or an aerial photograph of the building/site for marketing purposes.

Elevations

The drone can capture building elevation detail. This can then be vectorized to produced building elevations (similar to the process employed with our HDS laser scanning).

Discretion

Your survey will be undertaken by a qualified, experienced surveyor, working to the RICS code of ethics. We are very discrete & experienced with fielding questions from passers-by about developments. We are courteous at all times. We aim to minimise any disruption to the ongoing operational activies on site. We have experience working on secure sites such as care homes and schools. DBS (Enhanced) reports for our surveyors can be provided if legitimately required.

Pricing

We offer free fixed price quotations. We assume competive tender and give our best price based on our estimate of time & costs. Every survey is different, with a varying timescale (dependent on site size, logistics & detail) & travel costs.

Sustainable

We aim to undertake our quotations remotely to avoid unnecessary travel, in keeping with our Environmental Policy. We use Google Maps. This may not provide the full picture. So we are grateful if the client can provide photographs & a rough outline to show the extent of the survey area on plan. We also supply the finished plan electronically, in DWG and PDF formats. Though,we can provide paper copies at your discretion and convenience (see printing fee structure).

Terrain Models

 

Terrain Models

In addition to our traditional 2D land survey plans, we can offer a 3D element to the CAD model for the terrain.

3D Spot Heights

The first element is a 3D point for each ground spot level surveyed.

TIN

The next element is a surface of triangles (a Triangulated Irregular Network) derived from the 3D points.

Contours

From the TIN, we can then generate contour lines which are also presented in the PDF format.

Sources

We accurately orientate our land surveys to Ordnance Survey grid and to Newlyn (ODN) datum. The terrain data need not be limited to our Total Station survey. We also offer level-only surveys and 3rd party data integration, such as OpenData LIDAR.

GNSS Survey Orientation & Map Integration

 

Survey Orientation

Using GNSS RTK, we routinely orientate our surveys to Ordnance Survey grid and Newlyn datum. We can also orientate existing 3rd party surveys and measure the position of 3rd party survey markers such as UAV ground markers.

What is GSS RTK?

GNSS (Global Navigation Satellite System); receivers such as GPS in your car can triangulate your position to within metres. GNSS RTK (Real-Time Kinematic) ups the ante, with potential accuracy in the order of a centimetre. The device triangulates using up to 21 satellites & utilises a remote RTK network service to fine-tune accuracy in real-time.

Investment

We made the high capital investment in GNSS RTK in 2009, when we saw this technology's potential.

Survey Orientation

We can capture the absolute positions of our land survey control points and then orientate the whole survey to Ordnance Survey (OS) grid and Newlyn datum (mean sea level).

Datum

Ordnance Survey guidance highlights limitations in the traditional Benchmark system. GNSS RTK is generally quicker & safer than traversing to the nearest surviving OSBM, which could be kilometres away. GNSS RTK datum acquisition does not impact on the high relative accuracy of the local survey levelling; we use a single datum (as per RICS 'Virtually Level' guidelines).

Plan Orientation

Given the widespread use of the Ordnance Survey grid space by the Land Registry, Environment Agency, DEFRA and Local Planning Authorities, it often makes sense to orientate land survey plans into this space for consistency.

Our survey plans are oriented to the GNSS controls using a specialised software process with quality controls. It employs a least-squares best-fit approach with no relative deformation, so there is no loss in the high relative accuracy of our Total Station survey. The local survey can be scaled to OS local scale factor, if required.

Post-Orientation

We can also measure the co-ordinates of control stations of existing 3rd party surveys and UAV ground markers. We can re-orientate a local-grid survey to OS grid. We can also shift the datum of an arbitrary datum survey to ODN using our in-house CAD tools.

Map Integration

We have experience and capability integrating different map data. We routinely overlay and combine OS data, Defra habitat maps, Local Plan spatial models, deed plans and 3rd party plans such as proposed highway improvements.

Levels Surveys

 

Levels-only Surveys

Levels-only surveys is a Value Management consideration. A full topographical survey might not be necessary. For a preliminary Environmental terrain study, for example, it may be adequate to simply acquire a grid of spot levels and then overlay them to an existing map or plan, such as a licenced OS index map extract or a Title Plan.

Sustainable

Using existing map data represents a sustainable approach by avoiding an unnecessary re-survey of documented detail and can provide a relatively large financial saving of as much as 80% over a full topographical, even accounting for OS licencing costs. Should a detailed survey be required at a later stage, we can easily integrate the two separate surveys since our topographical surveys are geo-positioned with GNSS RTK.

GNSS RTK Grid Levels

We use our in-house process to plan a route for capture of the spot levels at required grid centers. This is uploaded to the GNSS RTK device. On site, the Surveyor is guided to each position in turn to quickly and efficiently capture each ground level. The surveyor can then freely capture levels at other key positions such as changes in gradient.

The GNSS RTK equipment constantly monitors the variable accuracy of the measurement. We use the in-built automatic quality-control thresholds to ensure that levels are not recorded unless they are within RICS and client specifications. Here we incorporate Total Station measurement where necessary when the GNSS RTK accuracy is generally sub-specification or there are issues with satellite or mobile phone coverage in parts of the site.

UAV / Drone Levels

To prepare a grid of levels from UAV/Drone point cloud, we have in-house, custom GIS tools. The levels can be created at any point in the site where there is clear ground cover, adding flexibility.

Terrain Models

We can also generate terrain models or contour lines.

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01903 267883

Offington® is a trading name of Offington Land Surveys Ltd. Registered in England&Wales no.3746387, Regd. Office 15 Cherry Tree Close, Worthing, West Sussex, BN13 3QJ. VAT number GB737003752. RICS and other 3rd party logos are registered Trademarks used with permission.

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