Cadcorp and OS MasterMap FAQ's
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This
document contains the answers to frequently asked questions (FAQ)
about Cadcorp and OS MasterMap.
Questions in this FAQ:
- What options do I have for using
OS MasterMap with Cadcorp?
- Why is my OS MasterMap overlay
not displaying any symbols?
- How should I order my OS MasterMap
data?
1)
Question: What options do I have for using OS MasterMap with Cadcorp?
Answer:
OS MasterMap Index
This method allows users to quickly view the spatial extents of
their OS MasterMap coverage without actually opening the data.
Native GML
OS MasterMap data in its native delivery format can be viewed directly
in SIS. Users can open data on a chunk by chunk basis. The data
can be copied in to an editable overlay for local use. Change Only
Update data can also be opened as an independent overlay.
The Cadcorp SIS OS MasterMap Loader can load OS MasterMap (Topographic)
data (including managing Change Only Update with support for archiving)
into the following databases:
Oracle
Data is loaded into an Oracle table with the geometry object stored
using Oracle’s SDO_Geometry type. Spatial data can be queried
and spatially analysed using SQL.
Recommended use: corporate use for large organisations (50+ concurrent
users) with up to national level of coverage.
SQL Server
Data is stored in SQL server tables. The geometry object is stored
using the Image data type. Attribute data is held in normal columns
and can be interrogated using SQL. SQL Server 7 does not support
server side spatial analysis.
Recommended use: corporate use for medium size organisation with
up to 50 users. Recommended database size is up to regional cover
(approx. 5 million geometry features).
Access
Data is stored in an Access database (up to a limit of 2gb). The
geometry object is stored using an OLE Object data type. Attribute
data is held in normal columns and can be interrogated using SQL.
Access does not support server side spatial analysis. Microsoft
Access does not have to be loaded in order to use this storage format.
Recommended use: Personal database for small volumes of OS MasterMap
(up to approx. 2 million geometry features).
2) Question:
Why is my OS MasterMap overlay not displaying any symbols?
Answer: If
your OS MasterMap overlay is not displaying the correct symbols
check that the overlay is a mapped to the OSDNF Advanced feature
table.
Ensure that the overlay map scale has been set correctly, OS MasterMap
overlays should be set to a scale of 1250. Bear in mind that there
is a relationship between the map scale and the current view scale,
if you expect to see line thickness of 5mm thickness and a scale
of 1250 then at a scale of 2500 the line thicknesses will 2.5 mm.
If the MasterMap overlay is editable the scale can be set from the
Dataset tab on the Overlays dialog box. If the overlay is not editable
then you must use the override option under the Styles tab of the
Overlays dialog box. Once the overlay has been saved it will maintain
the scale setting when the swd is opened on another occasion. You
can access the Overlays dialog by going to Map – Overlays,
or by pressing F2.
3) Question:
How should I order my OS MasterMap data?
Answer: With
the introduction of the new MSA and the online ordering service
for OS MasterMap data, Cadcorp customers should follow the following
procedure when ordering data from Ordnance Survey.
Each customer will require a 'contract' with the OS
to order any data. Once this 'contract' is established, any number
of 'orders' can be processed by the customer. The OS will, by default,
supply OS MasterMap Topographic and OS MasterMap ITN data in a set
of single gzip files for the size specified (2km, 5km or non-geographic
chunking). This means that all gzip files in this order will contain
both ITN and Topographic data.
Cadcorp requires that all OS MasterMap products are
supplied in separate gzip files. Topographic data and ITN data must
be supplied in separate files. To do this, Cadcorp customers must
set up separate 'orders' for Topographic and ITN data within their
'contract'.
ITN Data
ITN data is currently supported by reading this data dynamically
through the standard Cadcorp SIS interface. Cadcorp currently does
not support Change Only Updates for ITN data. Customers must order
a complete re-supply of their ITN data. Cadcorp is currently developing
an application to manage the use of road routing information within
ITN data.
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Technical
FAQ's |
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