Questions and answers

Find common questions and answers about the LINZ Data Service and the datasets you can access through it.

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Hydrographic data

What hydrographic data is currently available from the LINZ Data Service?

The following hydrographic / maritime data is available:

  • Data based on official Electronic Navigational Charts (ENCs) published by the New Zealand Hydrographic Authority Prior to loading onto this service, the S-57 data from these ENCs is converted to shapefile format.
  • Digital maritime boundry definitions for New Zealand.

Where can I obtain official Electronic Navigational Charts (ENCs)?

For navigation, mariners should use official New Zealand ENCs - find out where to obtain ENCs.

Can data from the LINZ Data Service be used instead of Electronic Navigational Charts (ENCs) for navigation?

No. This data:

  • does not replace official ENCs
  • should not be used for navigation
  • is not corrected for Notices to Mariners.

Where can I find more information about feature and attribute codes used in the hydrographic data?

Feature and attribute codes used are based on the IHO S-57 standard. Links to these documents are available from Hydrographic Standards and Regulations.

Why is continuous coverage of hydrographic data not available at some scales?

Coverage of data is limited to the extent of current published Electronic Nautical Charts (ENCs). Further data will be published on the LINZ Data Service as new ENCs are released.

What horizontal datum is used for the hydrographic data?

World Geodetic System 1984 (WGS84).

What sounding datum is used for the hydrographic data?

Approximate Lowest Astronomical Tide.

Geodetic data

What layers of geodetic data are available in the LINZ Data Service?

Find general information about the geodetic datasets available.

Where do I find more information on geodetic data found in the LINZ Data Service?

See the geodetic system webpages for full and comprehensive information on geodetic data, datums and coordinate conversions.

Why is Antarctic data included in a separate layer?

The Antarctic data is referenced in terms of Ross Sea Region Geodetic Datum 2000 (RSRGD2000) which covers the extent of the Ross Sea Region in Antarctica. The NZGD2000, which is the datum for the majority of geodetic data, only covers mainland New Zealand and off-shore islands.

What is the difference between the 'geodetic marks' and 'geodetic vertical marks' layers?

The geodetic marks layer includes information about all geodetic marks in the region, whereas the vertical marks layer includes information about all geodetic marks that have heights in terms of a local mean sea level datum.

What is the geodetic survey control marks layer used for?

This layer includes the geodetic marks which have been broken down into principle control networks. Each of these classifications has governing standards which make marks within these networks fit for a particular purpose. See survey control networks for more information.

Does the LINZ Data Service have orthometric heights?

The Antarctic geodetic vertical marks and geodetic vertical marks layers contain information for all geodetic database marks that have orthometric heights.

The geodetic database also contains a large number of marks that only have ellipsoidal heights. These heights can be converted to orthometric heights using NZGeoid09 and the online coordinate conversion application. In the future, LINZ will automatically include these calculated orthometric heights in the vertical marks layers.

Aerial imagery data

What is aerial imagery?

This is imagery collected by airborne sensors and cameras, and provides an accurate representation of the earth’s surface and features on it.

What imagery is available?

New Zealand’s most current publicly-owned aerial imagery, covering 95% of the country has been unlocked for public access and is now available on the LINZ Data Service (LDS).

What areas does it cover?

This imagery covers almost all of New Zealand. It is generally the more remote area where imagery is not available, such as mountain ranges.

How do I access this imagery?

This imagery can be viewed and downloaded from the LINZ Data Service website.

How is this imagery collected?

Aerial imagery is captured from airborne sensors and cameras. For decades, local government as well as central government agencies have purchased this imagery for managing land, and for making decisions about locations. This will continue to be gathered but procurement will be more consistent across government, and will ensure that it is open licensed so anyone can use it.

What are the specifications of this imagery?

All the imagery on the LINZ Data Service is orthorectified imagery. The resolution varies based on the age and the requirement of when it was captured. Please refer to the metadata for each layer for specifics.

Will you be making the imagery available as a map service?

LINZ will be trailing map services in the near future which will include imagery data. Stay tuned for more information in the LDS newsletter.

How does it differ from Google earth?

This imagery has been adjusted to remove shadows and other obstructions, and is licensed so everyone can use it. While Google Earth has a lot of uses, it has some limitations such as a lack of metadata like date and accuracy information, which means it cannot be used for industries such as land development and agriculture, in the same way that this imagery can.

Who can use this imagery?

Aerial imagery has a wide range of uses both for the public and private sector. There is an immediate benefit for councils in planning and resource management, while forestry and agriculture industries can use aerial imagery to help get better productivity out of the land. Aerial imagery is also a useful tool for planning construction and engineering works, and for managing large areas of land. Other uses include disaster recovery planning, archaelogy and land management.

Why do the aerial imagery layers overlap at the edges?

The imagery datasets have been captured in regional blocks and although capture is usually required to the council boundary, it is common practise for imagery to bedelivered in full tiles.

Are the imagery datasets colour balanced?

Each dataset is colour balanced as a set but not colour balanced to any other aerial captures. This is due to the fact that other aerial captures may have occurred in different years and by different aerial capture companies.

Will this imagery be updated?

LINZ has worked with Local Government to ensure that as they purchase new aerial imagery it will be made available on the LINZ Data Service on an open license at a consistent standard. LINZ will endeavor to provision data within a few months of acquisitions being delivered.

At this stage, there is no official maintenance cycle and updates are tied to regional funding and procurement cycles.

What is the benefit in making this available?

In the past, this imagery has been hard to find or access even when needed for rebuilding in Canterbury or for emergency response situations. Making it available on an open license and accessible through the LINZ Data Service should solve this problem, and reduce the chance of agencies doubling up on the imagery created. It also makes it available for industry to use and for use in creating value added products like smartphone apps.

Do you have archival imagery?

LINZ will be investigating the potential to make archival imagery more accessible in a similar way to this aerial imagery. However, until then people will need to contact Archives New Zealand for archival imagery.