Mapping of known elevation points of Lorient Agglomeration (canvas points)

These data identify the points of canvas from the Reference to Very Large Scale of Lorient Agglomeration (RTGELA). A topographic canvas point is a perennial, materialized and georeferenced reference point, used as a basis for topographic surveys. These points make it possible to guarantee the accuracy of topographical measurements, to control and verify existing surveys. They make it possible to link new surveys to the legal reference system in planimetry (RGF 93 CC48) and altimetry (IGN NGF 69). **Collection context** The majority of the points come from topographic surveys or surveys ordered by the services of Lorient Agglomération or the member municipalities. These surveys were previously validated by the SIGT Mission on the basis of a form and precision check. Some points were implemented directly by the SIGT mission. **Method of collection** Points are georeferenced in planimetry from targets by tacheometer on existing points or by GNSS if there are no existing points. Altimetry is systematically determined by the direct leveling method from existing points and/or IGN markers. Each canvas point is the subject of a station sheet detailing the characteristics of the point and enabling it to be easily identified on the ground: coordinates to the mm, photograph, location plan, side drawings, nature of the point, address, etc.). The points are checked on an ad hoc basis in the field by the SIGT mission according to the size of the survey (large-scale fitting-out operations, sewerage networks, etc.) in accordance with the requirements of the Order of 16 September 2003 (published in the Official Journal of 30 October 2003) concerning the classes precision work applicable to categories of topographical work. **Attributes** | Field | Alias | Type | | --- | --- | --- | | `id _canevas` | PK primary key num auto | `int4` | | `id _tronçon` | canvas _pct _id _tronçon _fkey | `int4` | | `preci _plan` | Planimetric accuracy em mm | `int4` | | `preci_alti` | Altimetry accuracy em mm | `int4` | | `link _pdf` | Link station file pdf | `varchar` | | `x_cc48` | coordinates X projected | `float8` | | `y _cc48` | coordinates Y projected | `float8` | | `z` | z Station | `varchar` | | `comments` | Miscellaneous comments | `varchar` | | `date _crea` | Auto calculation Date of creation (Do not complete) | `date` | | `date _modif` | Calculation auto Date modified (Do not complete) | `date` | | `idgeometer` | id of point from csv | `varchar` | | `_txt fiche` | Name of the txt file when importing | `varchar` | points | `adr_proche` | Nearest address (0 to 75m) | `varchar` | | `lien _jpg` | Lien fiche station jpg | `varchar` | | `id _case` | canvas _pct _id _case _fkey | `int4` | | `id _nature` | | `int4` | | `lib _nature` | | `varchar` | | "operational" | | "bool" | | `date _leve` | Date of survey | `date` | | `date _control _plani` | Date of planimetric control | `date` | | `date _control _alti` | Date of altimeter control | `date` | For more information, see [the Isogeo catalogue metadata](https://open.isogeo.com/s/0bd17a2a330842c68ec4a412d1df6824/AiCyPK6W8fg012l-vHV0s5tPry5b0/r/2feaf9d10b5443848afcd8ed1c79daf5).