Tag Archives: video

Aerial imaging

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Cost-effective environmental imaging services combining camera drone and cloud technology

As a drone pilot and operator registered with CAA in the UK I’m able to offer a variety of commercial services in open countryside locations, where a full PfCO is not required.

Mapping

On one privately owned site in the Surrey Hills AONB I mapped 32 hectares (79 acres) of part ancient, mixed broadleaf woodland.

Thousands of individual images were stitched together to create an orthomosaic, which was then exported as individual GeoTIFF tiles compatible with GIS software. Very high resolution single images can also be generated (2cm/pixel).

Mapping missions were flown at different times of year to observe seasonal variation.

Analysis

Spectral analysis techniques allow aerial imagery to be used for environmental monitoring at landscape scale. The image below compares visual spectrum vs. enhanced NDVI processing to study plant health.

Visual spectrum vs. NDVI showing replanted woodland

Change detection

Orthomosaic images facilitate accurate measurement to inform effective land management. The aerial map below quickly measured the extent of a heathland fire at Thursley Common NNR in Surrey for Natural England.

Aerial drone map showing extent of Thursley NNR heath fire

Monitoring

Below is an aerial survey of a Homes England residential development at the point where a new access road crosses a river valley intended to form a ‘green corridor’ for wildlife. Orthomosaic, NDVI and elevation visualisations are compared.

This short animation shows the image resolution (~2cm/pixel) attained from the same drone survey mission flown at an altitude of 100m.

Timelapse

By layering orthomosaic images created in different seasons it’s possible to create a wide area timelapse sequence, as shown below.

Video

More conventionally, the video below shows scenes from a Bluebell wood in early spring. Bluebells are an attractive ancient woodland indicator species.

Drone vs. satellite

Drones and satellites offer complementary technologies for aerial imaging, but camera drones enjoy a few advantages:

  1. Resolution
    Satellites cannot compete with drones for detail. Satellite images will allow you to see individual trees, but with a drone it’s possible to distinguish each leaf.
  2. Perspective
    Satellites are restricted to flat overhead perspectives. A well-operated drone can film or photograph any subject from almost any angle. This can assist in the capture of digital elevation models using 3D point clouds.
  3. Urgency
    You don’t need to wait for cloud cover to clear before flying a drone survey! If clouds obscure your satellite image you have no option but to schedule another attempt… and cross your fingers.

White Admiral Watch: Rollo’s Story

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A tale in tweets following the life of Rollo, a White Admiral butterfly caterpillar, offspring of Camilla

As Rollo slumbers a brief interlude follows…

We return to the star of our show…

Rollo’s close neighbour catches a chill…

Spring returns to the wood…

White Admiral Watch pays tribute to Eric Carle, author of ‘The Very Hungry Caterpillar’…

But not all is well…

The reason for Rollo’s delayed development becomes clear…

Search #WhiteAdmiralWatch on Twitter for more!

Raft Spider Life Cycle

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Raft spider on pond surface

Raft spider on pond surface

You’d think that arachnids and water was an unhappy combination, but one species of European spider has made boggy ponds their home.

The raft spider (Dolomedes fimbriatus) is the UK’s largest native spider – its body growing up to 2cm long.

It uses the water’s surface like other spiders use their webs – feeling for the vibrations of potential prey with front legs extended. Using this technique it hunts tadpoles, insects and occasionally small fish:

Raft spider eating damselfly

Raft spider eating damselfly

When alarmed, the water repellent hairs on the raft spider’s legs enable it to dive beneath the water, trapping a bubble of air to keep it alive until the coast is clear and it cautiously re-emerges:

The wetland pools favoured by raft spiders are increasingly rare in this country. On the RSPB’s Arne reserve in Dorset their habitat is lovingly preserved, and offers wildlife watchers easy access from the nearby heathland trail:

Boggy pond habitat

Boggy pond habitat

On a good day dozens of raft spiders at various stages in their life cycle can be witnessed at the pond’s edge.

1. Sex

The female raft spider is often considerably larger than the male and mating is a dangerous business. He approaches her cautiously, waving his front legs tentatively to judge her receptiveness:

Male raft spider approaches female

Male raft spider approaches female at her den

She may rush out to scare him off on numerous occasions, after which she retreats and the process begins again, the male edging closer all the while. It’s a nerve jangling thing to watch, let alone participate in.

2. Birth

The female spins a silk bag to contain the fertilised eggs, which she carries about beneath her body, keeping it just warm and moist enough to ensure their survival:

Raft spider carrying egg sac

Raft spider carrying egg sac

Then, when the baby spiders are ready to hatch, she lashes the egg sac to vegetation at the edge of the pond and the tiny hatchlings emerge:

Baby raft spiders in nursery web

Baby raft spiders in nursery web

Mum typically lies in wait nearby to ensure that her young ones don’t come to any harm:

Raft spider guards her hatchlings

Raft spider guards her hatchlings

This phenomenon of hundreds of spiderlings crowded together for their own mutual safety is only really appreciated up close:

Raft spider hatchlings

Raft spider hatchlings closeup

But soon the young raft spiders are large enough to fend for themselves and disperse around the pond.

3. Death

Raft spiders are not fussy eaters. When times are tough and food is scarce, or when too many raft spiders compete for the same local resources, they may even turn to cannibalism:

Not such a pretty sight!

Related links:

An Audience With The Purple Emperor

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Purple Emperor Banquet

Purple Emperor butterfly (Apatura iris) feasting on fresh dog turd

Such a beautiful creature with such un-photogenic habits! Infamously the Purple Emperor butterfly (Apatura iris) spurns the sweet nectar of wildflowers in favour of dog faeces amongst other delicacies.

Now mostly confined to the ancient deciduous woodlands of Surrey and Sussex in the UK, the Purple Emperor has a devoted following in the world of butterfly fans.

Normally it flies high in the woodland canopy and only occsionally will the male descend to the ground to replenish its liquids and salts in this peculiar fashion.

On these rare occasions the Emperor’s acolytes fill their boots.

Here on Bookham Common in Surrey, within sight and sound of the M25 motorway, the lack of a long lens is no handicap when this butterfly is distracted by a fresh deposit:

Purple Emperor Phone

Purple Emperor posing for a mobile phone photograph

The less exotically coloured female at least has more refined tastes, and generally remains high in the oak trees feeding on the sticky sweet honeydew secreted by aphids. She returns a little closer to earth only to lay her eggs in a suitable sallow tree nearby.

Purple Emperor Laying

Female Purple Emperor laying eggs on willow sapling

Such is the lure of the Purple Emperor that fanatics have been known to entice ‘His Majesty’ down from the trees with a number of foul smelling concoctions. In the absence of dung a rotting carcass may occasionally do the trick. This recently deceased rodent at a favourite butterfly haunt in the wood may have benefited from a coroner’s inquest:

Suspicious Death

Suspiciously well placed mouse carcass!

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Avocet City

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Symbol of the RSPB in the UK, the avocet was extinct as a breeding species by the mid 19th century, only returning to these shores during the second world war after the flooding of East Anglian marshes for coastal defence restored ideal wetland territory for the birds. Since then the reintroduction and careful managment of this scarce habitat elsewhere in the UK has proved to be a major conservation success story.

Hundreds of avocets overwinter on the south coast of England in Poole Harbour – the second-largest natural harbour in the world. In autumn they can often be found huddled together in the lagoon on Brownsea Island close to the busy shipping lanes at the harbour entrance. As winter draws on the birds seem to disperse, favouring the more sheltered harbour channels. The Middlebere channel to the south of the Arne peninsula is a particularly popular location.

Avocets in Poole Harbour

Avocets gather in Poole Harbour

My main goal on this day was to film and photograph some winter finches along the crop trail managed by the RSPB’s wardens on the Arne Reserve. However it quickly became overcast and I wandered off in the direction of Coombe Heath to see what wading birds were on the Middlebere channel instead. By the time I reached the viewing screens the clouds had cleared and a ‘raft’ of several hundred avocets was beautifully lit in the low winter sun:

Avocets

Raft of avocets on the Middlebere channel from Arne

Unfortunately the birds moved off before I could set up my tripod for video but one of the RSPB’s wardens kindly pointed out a sheltered spot near the shore where I could get a closer view of their new location.

As I sat and watched the light on the harbour just got better and better with each passing minute. The calls of the waders could be clearly heard in the still air and, as the tide turned, the raft of birds gradually dispersed in my direction, scouring the mud for tasty morsels:

Osprey Encounter

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Ospreys are regular visitors to Poole Harbour in the autumn, on route to Africa where they flee for the winter. These birds are especially well adapted for catching fish and extraordinary to watch.

We’re very lucky to have such magnificent neighbours but I’m not sure that many inhabitants of nearby Poole and Bournemouth realise they exist, let alone where to find them.

The National Trust have a wildlife hide at Middlebere on the edge of a channel running into the harbour. It’s tucked away in the woods opposite the RSPB’s reserve at Arne. In season the ospreys can regularly be seen commuting up and down the channel on fishing expeditions. Great to watch through binoculars and scopes, but for photographic purposes they remain a long way off.

Having watched them from the hide on a few occasions I became familiar with a regular perch nearby. It looked accessible and there was decent cover nearby, so I determined to get closer.

On more than one occasion I observed ospreys perched in the branches of a dead tree after arriving on site. However ospreys are quite happy to spend hours sat in the same location and are difficult to approach. This was the closest I managed to get with a long lens without spooking the bird:

Osprey in dead tree

Perched osprey (Pandion haliaetus)

To get any closer I was going to have to get into position early one morning, before the birds became active, and wait for them to come to me. Several times I hid my gear nearby, tripod-mounted camera at the ready, and waited fruitlessly for a bird to appear.

On this particular occasion I was late to arrive and could see an osprey already in position.

Osprey perched in dead tree

Osprey (Pandion haliaetus) in dead tree

Having snapped a few long distance shots I might have turned back at this point but they’re beautiful birds to watch, even at a distance.

By the time I’d crept to the next viewing position the osprey had flown, but I seized the chance to scurry into position deep in the reeds, close to the dead tree perch, and hurriedly assembled tripod, camera and improvised camouflage. Pulling the reeds back over my head I settled in for what I thought might be another long, uneventful afternoon.

But within 20 minutes I saw a large bird flying in low over the reedbed. Through the binoculars I could make out a large wriggling shape in its grasp. It could only be a returning osprey!

I ducked down out of sight and watched the perch on the camera’s LCD monitor. Nothing. Wrong branch! Swivelling the lens to the left brought this majestic osprey into focus, a freshly caught bass pinioned in its enormous talons:

Osprey with bass

Osprey (Pandion haliaetus) with freshly caught bass

Over the next hour I was privileged to watch this mighty bird devouring its meal at close quarters, and captured some memorable stills and video footage in the process:

Canon 550D | Canon EF 100-400mm f4.5-5.6 L | Adobe Premiere Pro

The reedbed was enveloped in low cloud or mist and – together with the hissing sound of the reeds in the gathering wind – the conditions heightened an already surreal, unearthly atmosphere. Something I will never forget.

Wasp Spider Invaders

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I stumbled across my first wasp spider (Argiope bruennichi) in the summer of 2008. We’d been mowing a road verge with the National Trust and whilst sweeping up the grass noticed this extraordinary looking creature:

Female wasp spider (Argiope bruennichi)

It’s not what you’d expect from a British spider – the distinctive black, white and yellow stripes give it a dramatic appearance, and at 2cm it’s fairly large – something you might imagine encountering in the tropics, shortly before it bit you and ruined your holiday!

Sure enough it’s a foreign invader, more commonly found in the Mediterranean and first recorded on UK shores in 1922. Since then it’s made the south coast its home and, as conditions have warmed, has spread steadily north in recent years.

The Isle of Purbeck is at the southern extreme of its range in this country so it must have been present for some while. The following summer the female spiders were present in large numbers in a meadow at Durlston Country Park outside Swanage and I photographed them a little hastily with my point-and-click at the time.

When I acquired a DSLR camera capable of HD video recording this year, and a decent macro lens, I decided the wasp spider invaders would make a good subject for a short video:

Canon 550D | Canon EF-S 60mm Macro | Adobe Premiere Pro CS4

I couldn’t find the spiders in the places I’d spotted them previously, but while clearing another fenceline with the National Trust we stumbled across this small colony living on the edge of Godlingston Heath on the Studland peninsula.

Over a couple of visits I shot some decent footage and stills at very close range with the 60mm macro lens. The conditions were a little breezy, which makes life difficult at very shallow macro depths of field but I’m pleased with the results.

Wasp spider

Wasp spider macro detail

Try as I might I could not track down the male wasp spider, which is smaller and quite dull in colour. I would also have liked to include some footage of the spiders’ large egg sacs, but the weather turned wet and stormy towards the end of the month and by the time I returned the colony was washed out. Only a couple of females remained and no egg sacs.

Burnet Bodysnatchers

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Caterpillars get a raw deal.

It’s true that the lucky winners in life morph into fabulous winged creatures which transcend their earthy origins, but a great many of their brethren seem destined to become nothing more than a convenient snack for any number of passing creatures.

Walking along the Purbeck coastal downland in mid summer I discovered a particularly unpleasant variation on this theme.

I was hoping to photograph some Adonis blue butterflies – a local speciality – but became mesmerised by a collection of tiny cocoons fastened to a grass stem. The more I looked, the more cocoons I found, but all appeared to have been vacated.

I couldn’t think what they might be, until additional exploration eventually uncovered their unfortunate victim nearby: a burnet moth caterpillar, seemingly tied to the stake:

Burnet caterpillar with cocoons

Burnet moth caterpillar parasitised by wasp larvae

This time the larvae were all too evident, as they appeared to be burrowing out of the caterpillar’s skin!

Further research reveals a fascinating tale of nature’s indifferent ingenuity:

The perpetrators in this instance are a species of Braconidae wasp which lay their eggs inside caterpillars.

When they hatch the larvae consume the caterpillar from the inside, but are careful to spare vital organs in order to keep their victim alive. Eventually the larvae cut their way out using specially adapted sharp mouthparts. When they emerge they immediately spin cocoons attached to the caterpillar.

Recent studies suggest that the larvae influence the caterpillar’s behaviour to remain in place and guard the cocoons. Thus brainwashed, the creature may even spin it’s own silk around the cocoons to further protect them. The wasps later hatch and the zombified caterpillar dies of hunger. Ain’t life great!

The Braconidae wasps don’t get it all their way however, as another variety of Ichneumon wasp parasitises the Braconidae pupae inside their own cocoons.

I found an example of this behaviour a bit further along the same stretch of coastal downland. The cocoons had been deserted by their caterpillar protector for some reason, which left them exposed.

Parasitic wasp

Ichneumon wasp parasitising Braconidae wasp pupae