Questions about downloading aerial imagery from LINZ Data Service

[AdrianPetford]

I have been experimenting with photoreal scenery recently, as well as having a long-standing interest in aerial photography.

As has been mentioned in the Godzone forum, LINZ has just released recent, higher resolution coverage for the entire North Island, with the South Island to follow.

I'm now trying to download the 0.5m Auckland 2010-2012 coverage from the LINZ Data Service and have a few questions in relation to using it for possible FS photoreal before I get too far into the process.

1. Presumably the imagery is originally NZTM (New Zealand Transverse Mercator). Should it be left as NZTM and then reprojected later or saved as WGS84 when you set up your download?

2. I have previously used GeoTIFFs but these would multiply an already massive download size. JPEGs are the smallest files but are these still georeferenced? What is a JPEG2000?

3. The full download packages can only be ordered as they're over 3Gb in size, so I'm having to grab individual tiles. Is there any way to add individual tiles to your map so they download in 3Gb blocks?

LINZ Imagery

Thanks,


Ade

[NZ255]

1) It depends. I prefer to download the NZTM projection as that's what the full resolution is at then reproject it to WGS84. Of coarse there's probably no difference but I may like to use some of the imagery as a base for reference eg in a modeling program. Unless you have tools to reproject it later, you might want WGS84.

2) Unless you have tools to save to as a GeoTiff you'll need to download it as a GeoTiff as that's what the resample tool requires. I have downloaded some JPEG200 (lossless) images as they are far smaller. JPG2000 is a newer standard of format that is more efficient in compression that comes in two flavors, lossy and lossless. If you want the highest quality, go for the lossless version.

3)You might just have to play around. If you have a tool you can have an overlap and it won't matter as you can export the entire image in one go (depending on how big it is) Try the crop tool set at TopoMap50 and select different regions?

Sorry for any spelling mistakes, it's 3:30am....time for bed!

[Ian Warren]

QUOTE (NZ255 @ Mar 23 2014,3:29 AM) <{POST_SNAPBACK}>

Sorry for any spelling mistakes,

I just shrug me shoulders , people called it Ianglish so must be true or I simply blame it on Marsbar

QUOTE (AdrianPetford @ Mar 22 2014,11:18 PM) <{POST_SNAPBACK}>

I have been experimenting with photoreal scenery recently, as well as having a long-standing interest in aerial photography.

What region are you looking into Ade ?

[AdrianPetford]

QUOTE (NZ255 @ Mar 22 2014,2:29 PM) <{POST_SNAPBACK}>

1) It depends. I prefer to download the NZTM projection as that's what the full resolution is at then reproject it to WGS84. Of coarse there's probably no difference but I may like to use some of the imagery as a base for reference eg in a modeling program. Unless you have tools to reproject it later, you might want WGS84.

2) Unless you have tools to save to as a GeoTiff you'll need to download it as a GeoTiff as that's what the resample tool requires. I have downloaded some JPEG200 (lossless) images as they are far smaller. JPG2000 is a newer standard of format that is more efficient in compression that comes in two flavors, lossy and lossless. If you want the highest quality, go for the lossless version.

3)You might just have to play around. If you have a tool you can have an overlap and it won't matter as you can export the entire image in one go (depending on how big it is) Try the crop tool set at TopoMap50 and select different regions?

Sorry for any spelling mistakes, it's 3:30am....time for bed!

Thanks Nick, that's really helpful. As a result of this as well as messing around, I've decided to stick to my usual workflow and go for GeoTIFFs in NZTM. I collect aerial photography anyway so the FS angle is only one possible use of the imagery. I'm downloading them in blocks based on the georeferencing, reprojecting and then compiling the BGLs based on the same georeferencing which should help to keep the file sizes down. I've already covered Auckland coast to coast with 50cm scenery and it's only used 3Gb so far, and that's with the GeoTIFFs kept at maximum resolution. Very impressed!

Cheers,

Ade

QUOTE (Ian Warren @ Mar 22 2014,8:40 PM) <{POST_SNAPBACK}>

I just shrug me shoulders , people called it Ianglish so must be true or I simply blame it on Marsbar


What region are you looking into Ade ?

I'm just sticking with Auckland for now as still learning. If I get any good I quite fancy having a go at a photoreal Dunedin.

The new imagery is outstanding so we should be spoilt for choice picking good areas for scenery now

[Ian Warren]

Dunedin would be a good spot, Auckland is super huge, may ware you out , so many places you can pick on

[toprob]

I normally download JPEGs, in NZTM. These come with a World file (.jgw) with the geoTIF coordinates. Once they are converted into a BGL I can't see any difference between starting with a TIFF or a JPEG. (BGL compression is a lot higher than the supplied JPG compression.) Since the aerials are normally soft, they work well as JPGs, you just need to give them a good unsharp mask.

I've downloaded a lot of these this week, and it is clear that larger chunks can be problematic -- I actually aim for chunks no bigger than 1GB, otherwise I'm likely to either wait a couple of days for confirmation of the download, or I'll get an email saying there's a support ticket created for that download, in which case I have to start over. This may be because I work normal hours, though, outside these hours you may get a better result.

Some areas I just haven't been able to get, either the download creation process just freezes, or I get an error email. However I didn't get any of these downloading Auckland.

[toprob]

Their server definitely works faster on the weekend, both building and serving downloads, that's for sure.

[toprob]

I just read Nick's reply in detail, rather than just skimming, sorry Nick, and he gives a lot of comprehensive info.

Overlapping isn't a problem, unless you extract everything into one folder -- some tiles will have the same name, but will be different depending on the crop, so I extract to separate folders and combine them in Global Mapper.

(My plan resets in 4 days, so I'm running on fumes at the moment...)

[NZ255]

If anyone's interested I'll be heading along to the LDS presentation on Thursday 4th of April. I'll post my findings afterward unless it's published.
http://www.linz.govt.nz/about-linz/linz-da...14#Presentation

[dbcunnz]

QUOTE (NZ255 @ Mar 27 2014,2:36 PM) <{POST_SNAPBACK}>

If anyone's interested I'll be heading along to the LDS presentation on Thursday 4th of April. I'll post my findings afterward unless it's published.
http://www.linz.govt.nz/about-linz/linz-da...14#Presentation

Hi Nick I would be interesting to know if they are going to get and have the southern alps photo images in the future, I would love to have it to add to the West Coast towns I am currently working on

[NZ255]

Unfortunately I wasn't able to make it to the presentation but it's available here if you're interested:



"South Island coming in the next few months"

[toprob]

We're starting to see some more South Island images now, although mostly lower resolution stuff -- 75cm to 1m. Still, a huge improvement over previous LINZ offerings.

[NZ255]

Almost all coverage as of now

[toprob]

QUOTE (NZ255 @ Apr 28 2014,11:09 PM) <{POST_SNAPBACK}>

Almost all coverage as of now

Yes, but I'm wondering if that could be all we're getting for the South Island. The North Island is at least 50cm or better (lots of 30cm and higher), except for Northland, but most of the South Island is 70cm to 1m. Timaru is well-served with some 7.5cm. Christchurch relies on those early post-earthquake images, which are a good resolution but poor quality.

Still, for areas which I've previously done at 2.5 metres, even 70cm is a huge improvement. The West Coast images which Doug is using for his towns, and I'm using for the airfields, is 40cm, which kind makes it one of the better-served areas in the south. I was hoping for some airports to be within 10 - 20 cm areas, but I can't see a lot in the South Island. For instance, Otago is all 75cm, which rules out a high quality photo base for Dunedin airport at the moment.

Maybe there's more to come this week, or at least within my lifetime.

In the meantime there is plenty to be going on with, I'm like a kid in a candy store...

[Ian Warren]

It is superb the LINZ data is out there now, lot off work doing cutting areas out but the best example is the results on the west coast bleeding it into obrx or vlc .

[toprob]

There's certainly plenty of scope for your Canterbury town project, Ian.

[Ian Warren]

QUOTE (toprob @ Apr 29 2014,11:36 AM) <{POST_SNAPBACK}>

There's certainly plenty of scope for your Canterbury town project, Ian.

New hi res photo rather than painting black and whites, bleed the photos into both domains and autogened properly, be a superb collection and ideal for the VFR pilots.

[NZ255]

QUOTE (toprob @ Apr 29 2014,9:06 AM) <{POST_SNAPBACK}>

Yes, but I'm wondering if that could be all we're getting for the South Island.

Hopefully not, I know some councils are sitting on some nice imagery. Just a case of if they'll give it up.

[Ian Warren]

QUOTE (NZ255 @ Apr 29 2014,1:03 PM) <{POST_SNAPBACK}>

Hopefully not, I know some councils are sitting on some nice imagery. Just a case of if they'll give it up.

I would have thought councils now and these days getting it from the same source , got the imagery from the same place, like council office people they are drones and really don't know whether it is released or obtainable.

[dbcunnz]

This is what is available now you can send an external hdd to linz and they will place the images that you want on it for you free of charge all you need is a paid return package saves hours of downloading

http://www.linz.govt.nz/topography/aerial-...icenced-imagery