NPP VIIRS Specifications

Thursday, 1 November, 2012

After the earlier blog post on day-night imaging I was interested to see what the exact specifications of NPP VIIRS are…. the NASA site had been down probably because of the interest in Hurricane Sandy, however it now seems available again. But there is very little information on the sensor itself somewhat surprisingly - even the Raytheon spec sheet is quite spartan. So no farther forward although I hope we’ll get more details in the coming months.

Another Q: Landsat equatorial crossing time?

Tuesday, 30 October, 2012

I had another good question in class last week as to why the Landsat missions have/had a ~10am UTC equatorial crossing time. In fact the full list of satellite times are below (Source: wikipedia):

Landsat 19:30 AM +/- 15 minutes
Landsat 29:30 AM +/- 15 minutes
Landsat 39:30 AM +/- 15 minutes
Landsat 49:45 AM +/- 15 minutes
Landsat 59:45 AM +/- 15 minutes
Landsat 710:00 AM +/- 15 minutes



So why is that? Although I didn’t know, I thought it was something to do with optimum reflectance from the Earth’s surface in relation to the original mission objectives, and that it’s stuck ever since

I’ve asked a couple of colleagues and the consensus seems to be to acquisition (globally) of “good”, usable, imagery but that it’s a trade off between about solar elevation angle, cloud formation and dew/frost cover. As you see from the table above, later Landsats have progressively gone for slightly later times.

Some further comments include because it places the local time for most of the imaged land areas (primarily in the northern hemisphere) in the 10am-2pm range when the sun is at a high elevation (in order to minimize shadow). Additionally, there is a consideration for cloud. “Conventional wisdom” is that we avoidthe afternoon buildup of cumulus clouds over interior regions with the10am crossing time. This doesn’t necessarily help out in coastal areas though.

Thanks to those who answered my query and any further thoughts would be welcome!

Satellite imaging at night

Monday, 29 October, 2012

I was asked in-class this week about imaging the Earth’s surface at night…… does it happen? The short answer is yes, it can, but generally doesn’t for much of the Earth-resource imaging that takes place. Here are some instances where it does (and I’m using examples from the fantastic NASA Earth Observatory Image of the Day):

Astronaut photo: plenty of examples using a standard digital camera with a short focal length, wide f-stop and high ISO. I like this one of northern Europe (Nikon D3S digital camera using a 28 mm).

Thermal Imagery: if there isn’t much visible light around, use a different part of the EM spectrum. Thermal wavelengths are commonly monitored, such as this image of a lava flow in Chile.

Microwave Imagery: thermal imagery uses naturally occurring raditation at longer wavelengths than visible light and the strong contrast (at night) to the surrounding terrain allows “hot” objects to be visible. Microwave, in contrast, is at much longer wavelengths (mm to cm) and uses energy generated by the satellite to illuminate the Earth’s surface. This allows it to operate at night (and through cloud). I couldn’t find any nighttime examples, but this one shows an oil spill off South Korea.

NPP Day/Night Mode: NPP VIIRS (see earlier blog) has a day-night band (wide bandwidth) and can therefore operate at night to image clouds (particularly when there is moonlight) and auroras (EOID explanation). A good image of Hurricane Sandy.

These are them most common nighttime imaging techniques you’ll come across, however most Earth surface remote sensing is achieved using a sun-synchronous orbit and so not at night.

Livescribe in action

Saturday, 20 October, 2012

Following on from my last post introducing the LiveScribe pen I wanted to highlight some useful resources and functions, as well as demo my first two “pencasts”. So, without much ado:

Pencasts:
-at it’s simplest this is making your notes/recordings available online either as a Flash animation or interactive PDF
-the PDFs work great and an incredibly effective way to distribute notes
-there is an iPhone app, but no Android app. This is an almighty cock-up because Livescribe have been banking on Flash working on Android - which it doesn’t. So at the moment, Livescribe doesn’t work on Android
-look at other peoples’ training notes to get a feeling for the scope

Pencasting(with some tips culled from the Advanced Pencasting webinar):
-however pencasts are very exciting for the production of training materials. They in essence allow you to produce, with little time or expertise, a live animation. You essential create a “performance” of the learning materials you want to develop. The flexibility in pencasting (albeit with some restrictions) are amazing
-write a script - I’ll say it again, its a performance
-keep it short 1-3 minutes MAXMIMUM, one page only. They are learning “bites”
-write (draw) first, narrate later. You speak faster than you write
-this highlights one of the exciting aspects of pencasting - when replaying the audio your drawings are synced to them. This massively extends the creativity of the pencast
-pre-draw elements in ordinary pencil on the page; you then get it “right” on your first “take”
-think about your presentation page design in terms of (1) layout and (2) navigation points. You want your material to be easy to follow, visually appealing and have visual cues so viewers know where to click to access different parts of the audio
-pre-draw (with the Livescribe pen) “templates”; these remain static and visible from the beginning (in black) meaning you can animate around them with your audio synced
-“pause and pop”: record, pause, draw, re-start (tap pause to continue). This causes the drawing to “pop” within the synced audio. Visually effective
-“Annotations”: draw your marker, record your audio, stop. Then playback and add your drawing. As I noted above, drawings added on playback are synced to the audio!! It’s worth stopping and taking that in - it is an incredibly powerful feature
-“Simuls”: take the annotations idea and continuously replay your audio to allow you to draw and build up your animation
-Marker Page: when using the “Simuls” approach, each time you playback you touch the marker on your dot-paper. Put the audio on a second page and your drawing on the first page. This stops all your dots appearing. When you export the first page as a PDF all the audio will be with it.
-as promised my first two pencasts. They are a long way from perfect but hope you get the idea:
Basic Wave Theory (including the accidental typo!)
Particle Theory



Training:
SmartPen101: online training
Webinar Recordings: recordings of live training the intro and advanced pencasting are worth viewing if a little long winded at times.

Wake Island

Monday, 15 October, 2012

Quite a remarkable image of Wake Island…..clearly the economy is limited!!

Livescribe Echo Pen

Saturday, 13 October, 2012

Over the summer I bought a Livescribe Echo Smartpen to try out some digital note taking (a review and on Amazon). Believe it or not, I like writing and smartphones don’t cut the mustard here, whilst tablets still have a way to go to beat the convenience of paper. The Echo particularly caught my eye as it integrates audio recording in to the digital note taking which in my mind makes it a killer combination. Sit in a lecture and take notes whilst recording the audio. Want to hear what the lecturer was saying when you were writing a particular note? Simply tap the paper at the point and it starts playing it. Audio ceases to be purely linear with a content timeline mapped out in your notes making it very easy to access. You can also upload your digital notes (and audio) to the desktop application and, wonderfully, you can search for words in your text (clearly it does some handwriting recognition behind the scenes) and also convert the writing to text (but using the extra “paid-for” app).

How does it work? Well digital note taking on paper falls in to two categories - a clip on IR sensor that works on any sheet of paper or special dedicated paper that allows the pen to know which page you are on and where. Livescribe use the latter approach with a small camera in the tip of the pen that records the ink trace and compiles the 2D coordinates in to your handwriting. This means you have to buy Livescribe notebooks - I find this fine and think the product is very reliable as a result. Combined with the audio (and you can get a directional mic to plugin!) it is a killer product in the note taking market. In a business meeting a need a formal written/audio record? Use Livescribe? Clerking a meeting? Livescribe. Legal ramifications (lawyer, education etc) - Livescribe.

The basic pen comes with 2Gb of memory - not much if you want keep all your recordings with you but more than enough if you record, upload and store. And its cheap at ~£70 in the UK (recent price drop), although Livescribe themselves have gone very quiet which suggests a product range revamp.

I use it for
-use it for recording a lecture and making notes
-use it for taking notes from books
-convert writing to text (MyScribe plugin)
-user it to create multi-media animations

More in a follow-on blog entry.

Reuters remote sensing links

Thursday, 11 October, 2012

A slew of Reuters remote sensing links which is quite refreshing. Possibly worth pointing out that we are now in the middle of World Space Week, not that you’d know it! Amazingly it was established by the UN and has been running since 1999 - I’ve only just spotted it now thanks to a great info piece from the BBC about DMC. Anyway, back to the news:

SpaceX Rocket Glitch: big news that SpaceX had its first commercial cargo mission to the ISS, with a secondary mission to deploy a satellite. A partial engine failure on launch led to a failure to meet orbit and so deployment of the satellite in the wrong orbit. C’es la vie!
SpaceX Success: but the built in redundancy means that it still made its primary objective of ISS resupply.
China Mars ambitions: China has firmly set its sites on Mars with a plan to bring back a sample from the surface. Exciting times.

QGIS Plugins

Tuesday, 9 October, 2012

I was presenting at the Society of Cartographers last month (on LAAP for those interested). Mike Shand gave an “Introduction to QGIS” (some helpful links on that page) which reminded me that I had wanted to do this blog post…..namely that “as it ships”, QGIS is pretty powerful but if you want to run through a complete project workflow you’ll rapidly find yourself up against a brickwall. It’s not that it can’t do much geospatial processing, but rather a lot of this functionality comes as plugins that have been developed separately. My MSc students hit this in their spatial analysis module - they perform an analysis in ArcGIS and then re-do it in QGIS. So this year I asked them to collate a list of “must have” plugins. So here it is and please feel free to suggest additions:

1. fTools: vector data analysis and management
2. Table Manager: edits and deletes shapefile columns
3. Spatial Query: conduct spatial queries on vector layers
4. Plugin Installer: download and install python plugins
5. MMQGIS: manipulates vector map layers, including alot of CSV functionality.
6. SEXTANTE: provides front ends to SAGA, GRASS, Orpheo Toolbox, MMQGIS etc. Think ArcToolbox for QGIS (to be rolled in to QGIS 2.0)

Sometimes there is an issue with a particular build so its always worth trying the master nightly build over at the QGIS Wiki.

BBC In Our Time

Monday, 8 October, 2012

OK, think I’m a little slow to the party on this one (and not a great radio listener) but the BBC’s “In Our Time” presented by Melvyn Bragg is a great “ideas” discussion programme (Wikipedia entry). Just look through the archive which features all episodes from the first in 1999 as well as an RSS feed for all episodes since 2011. Donald Clark notes the power radio for dissemination; thiss is ideally suited to learning and, in combination, with internet playback/recording means you can save and review. Perhaps I’m just not particularly a radio fanboy, but I do quite like listening to podcasts so it may be more a case of marketing than anything else. Not easy in a crowded marketplace.

Anyway, well worth a look at the archive and Ill be pointing my students to the broadcast on Radiation.

DVD Backup

Saturday, 29 September, 2012

Every so often I want to backup a DVD or portion of a DVD from a disc and need a simple solution to do it (ideally open source!). So it’s worth recapping the two stages needed:

1. Copy the files from the disc: they are encrypted so you need software that will decrypt them (and sometimes merge the multiple VOBs to a single file). You can do this with DVDShrink which helpfully runs portable. If you select the reauthor option then you can clip on the section you want to grab. If your disc is partially damaged this won’t work so another option is to install DVD43 which actually intercepts Windows file calls to the DVD player and then decrypts the files on the fly which means your software in step 2 should work

2. Author the files to your desired format. DVDShrink can compress the files for you or you can use something like MPEG Stream Clip to do the same thing. This would also allow you to demux if you just wanted the audio or video.

East Midlands Trains Wifi

Friday, 28 September, 2012

The good people at East Midlands Trains run an occasionally satisfactory service that I sometimes frequent. They offer free wifi which really must be a relatively “no cost” service for them to provide. For First Class passengers this is free probably because it provides some differentiation and excuse to charge the higher price tickets. Anyway (and thanks son!) their trains have mixed first/standard class seats which means, if you share the coach, you share the wifi. It works well, varies between fast and slow broadband speeds and operates in tunnels. All-in-all better than relying on mobile. It’d be interesting to know what the contention ratio is like and, in fact, what connection they use out on to the wired network. Useful tip of the week!

Open Dyslexic

Thursday, 27 September, 2012

Nice article at the BBC on Open Dyslexic….openly accessible fonts (and associated software) to make screen reading easier for dyslexics. Very good.

DVB transmission to archived XVID

Tuesday, 25 September, 2012

I had recorded a short clip off the TV using my Humax box - once your Hummy is connected to a network, with UPnP switched on, it’s easy enough to copy standard definition recordings straight off the box on to your PC (see previous post). These come off as .TS files, but this time I had a load of aggro trying to archive them to XVID. Not sure why and VLC wasn’t playing the file either. Anyway, after a fair bit of head scratching this workflow seems pretty good:

1. Split (demux) the .TS in to constituent audio and video streams using ProjectX
2. Combine (mux) the streams in to an .MPG (using .MP2); use MPEGStreamClip
3. Transcode the file using Mencoder
4. Play using SM Player Portable

Large FAT32 hard disk drives?

Monday, 24 September, 2012

If you order an external hard disk drive (HDD) chances are it’ll come formatted using NTFS. That makes sense as it’s an up-to-date system, however it isn’t so easy to use when you want to switch between different OSs. For those that want to use FAT32, which is well supported, then they hit a wall in Windows as formatting only supports up to 30Gb. Well that’s an artificially imposed limit by Microsoft. Simply use FAT32 Format and it’ll do the job.

Nice

New term, new students and…. new digs

Saturday, 22 September, 2012

Yes, that time has come, the first offspring departed for University and a new educational frontier (at Keele) awaits him. Across the country students are turning up with car loads ready to embark on a new life in charge of their own living. And digs are an inevitable part of that, be they university based or private. As a regular academic conference goer I get so see a variety of university accommodation (Swansea, Loughborough, Cork, Royal Holloway etc) and I can honestly say that Keele ranks at the bottom of this….by some margin.

See the university page for Lindsay Hall and compare it to the photos I took today….. very old furniture, a prison bed, plastic curtains and a heavily stained carpet with holes cut in it (presumably for long gone furniture). Its a 1960s build (not uncommon in the UK), however it looks like it was last decorated in the 1960s. Its cheap and its not really that cheerful. OK, its part of undergraduate living and with a few posters on the wall and the heating on and a few beers inside it doesn’t feel quite so bad (just as well I didn’t take any pictures of the showers).

But really, Keele, is this the best you can do for students being charged £9000 to study with you?? We expect all universities to make the grade in the UK, so quality of living is becoming a differentiator. To add insult to injury the radiator leaked, the electricity didn’t work, there was no phone and the woefully low strength aerial meant no digital TV (with the alternative of internet based Freeview over a bandwidth throttled connection).

It’s perhaps unfair to single out Keele - the digs we use in Swansea for fieldwork aren’t great and there is much variability across all campuses, with most having new builds with very nice accommodation. But there is no excuse for leaving living accommodation in this state - the world has moved on.

Google Cloud access to Landsat archive

Saturday, 22 September, 2012

This is a nice catch on accessing the Landsat archive. As with all things Landsat, its organised by path/row of individual scenes. Use the NASA convertor to work out which path/row you are interested in. You’ll then see a list of scenes with numbers such as this: LE70592202007107EDC00. The file contains ALL the bands in the image but encoded in name is the sensor (LE7 or Lndsat 7), path/row (059/220), scene date (2007107; think there must be a digit missing here or its an abbreviation) and source (EDC or Eros Data Centre).

Once you’ve got the file use 7zip or similar to decompress/unarchive. This will give you a series of files (band designations here) such as:

L71059220_22020070417_B10.TIF
L71059220_22020070417_B20.TIF
L71059220_22020070417_B30.TIF
L71059220_22020070417_B40.TIF
L71059220_22020070417_B50.TIF
L71059220_22020070417_B61.TIF
L71059220_22020070417_MTL.TXT
L71059220_22020070417_B62.TIF
L71059220_22020070417_B70.TIF
L71059220_22020070417_B80.TIF

These are bands 1-5, the two thermal bands (low gain and high gain) and band 7. Band 8 is the higher resolution (15m) panchromatic (read: B&W) band. If you are using these in a remote sensing package such as image you’ll need to layer stack them.

Go grab as its quick and easy once you know what you’re looking for.

Android App Update

Friday, 21 September, 2012

String of recent app updates that are worth a mention:

Mapdroyd: my favourite offine maps. Yes, offline, on your device, using full street level data from OSM. They’ve now moved to version two, a complete re-write using a new data format that, amongst other things, allows street/place searches. Better than before - a must have.

k9 Email: fantastic email client for those in the know. Not on Play, but Google code. Very regularly updated and now with a swish new interface. Nothing else worth a look.

TouchPal: as a longtime Swype user I have been disappointed at the bloat (17mb) and, more recently, the extremely laggy keyboard. It has gone from great to broken. There are now a few alternatives around and TouchPal is particularly good. Lightweight (4mb), lightning fast and flexible.

Perfect KAP camera??

Thursday, 20 September, 2012

Well, Nikon made a big splash by announcing the D600, the first consumer level full-frame (FX) DSLR (and plenty of reviews). Full frame is the key point and as cameradebate.com note, you get a bigger sensor which has four benefits:

No cropping of the image when using a 35mm compatible lens
Achieve shallower depth of field
Higher sensitivity and less noise (aka better high ISO performance)
Higher Dynamic range
Bigger and brighter optical viewfinder

The key point is that a full 35mm sensor is fitted in the lightweight magnesium alloy/polycarbonate body, almost the same as the D7000. This reduces the size and weight; its 760g as opposed to the 1000g of the D700.

Is this the perfect KAP camera? Well maybe - it has the high geometric fidelity and ability to use high quality lenses that we found when shooting with the D70. More importantly it has much greater sensitivity meaning that you can shoot at fast shutter speeds and high ISOs to obtain much sharper images, crucial for high quality photogrammetry. The ability to create high accuracy DEMs is significantly enhanced and the 24 megapixel resolution places it in a league of its own. Next step is to see if Nikon are willing to let me hang one underneath a kite!!

KAP Camera Coverage

Tuesday, 18 September, 2012

When mission planning for a Kite Aerial Photo (KAP) survey it’s useful to know the approximate coverage of each photo and pixel size. These parameters are basically reliant upon sensor resolution, flying height and lens type or more specifically:

-sensor size (width/height in millimetres)
-sensor size (width/height in pixels)
-lens focal length
-flying height

When I started my KAP work back in 2005 I wanted to calculate these automatically and Clive Boardman at Photarc Surveys kindly sent me an spreadsheet he used for mission planning. So I thought I would make it available as it’s incredibly useful. For my use I enter the the flying height which lets me see the image dimensions and pixel size. Enjoy!

Open Source GIS Conferences

Saturday, 15 September, 2012

Well it’s conference season and Claudio, the researcher on the NERC funded project I am working on, has been presenting some of the outcomes of the work. Specifically we have been using open source software and data to develop a web mapping application so it seemed appropriate to present at the two main Open Source GIS conferences in Europe this summer:

Open Source GIS Conference: held at University of Nottingham, this is building up a head of steam and the conference programme is pretty good (here are the abstracts). As open source becomes ever more pervasive in both business and academic contexts I think we’ll see this develop more fully.
Open Source Geospatial Research and Education Symposium: only the second one of these, being held in Lausanne, but the programme has arguably drawn and wider and richer body of work than OSGIS. Extended abstracts to be published shortly.

Not forgetting the grandaddy of course:
FOSS4G: …..and its coming to the UK in 2013 (specifically Nottingham). And, in fact, its a double-header coming immediately after AGI GeoCommunity

The other two main GIS conferences are GISRUK and AGI GeoCommunity. Both worth a look.