Heather Sharp
Live reporter

That brings our live coverage to a close. We hope you've enjoyed delving deeper into the tools and practices used by BBC Verify to analyse images and data.

Thanks for all the interesting questions sent in by readers and many thanks to our BBC Verify colleagues Erwan Rivault, Daniele Palumbo, and Ukrainecast presenter Vitaly Shevchenko, who have talked us through the expertise and technology they use, as well as answering your questions.

Of course it's not just big investigations these tools are used on - as I write this, BBC journalists are using these types of techniques to work out a bit more about the reports we mentioned earlier - that Ukrainian soldiers have crossed into the Russia region of Belgorod.

• If you want to read more about how BBC Verify identified extensive defences built by Russia in preparation for a Ukrainian counter-attack, click here.
• If you'd like how and why BBC Verify has been launched, click here.
• And for the latest updates on Russia's war on Ukraine, click here.

Today's live page was written by Malu Cursino, Gem O'Reilly, Alys Davies and Luke Mintz. It was edited by myself and Emily McGarvey.

How is BBC Verify funded?published at 14:08 British Summer Time 22 May 2023

14:08 BST 22 May 2023

One more question from a reader - Michael Lewis from St Albans in the UK asks:

Can BBC Verify provide details of who is funding the Verify department? Is there any funding provided by the UK government, Ministry of Defence or Foreign and Commonwealth Office?

Richard Burgess, the director of news content at BBC News, has replied to this one:

The BBC always strives to be impartial and is completely editorially independent.

You can find out more about how we are funded here and here. BBC Verify brings together colleagues from a series of BBC News teams - Data & Analysis, World Service Languages and BBC Monitoring Disinformation journalists, and verification specialists from User Generated Content.

How were these satellite images collected?published at 14:05 British Summer Time 22 May 2023

14:05 BST 22 May 2023

Erwan Rivault
BBC Verify

Another question - Daniella from Norfolk asks how the images in our investigation were collected.

Erwan Rivault replies:

We mainly use Planet Labs, a US commercial company with a constellation of more than 150 satellites observing planet Earth.

We use them alongside other providers (both commercial and open source ones), like Maxar Technologies and the European Space Agency (ESA).

Many of the images we gathered for this report were from Planet Labs, as they provide daily images from across the globe. Once we've searched for our area of interest, like the beach in Crimea, we move on to prioritise the most recent images - avoiding the cloudy ones.

Once we are happy with the quality of the image, then we move on to exporting it and crop the image to the area we want to focus on.

At this stage, my data visualisation skills come in and I add the necessary labels to guide the viewer and pinpoint any interesting features that will add insight to the story.

Vitaly Shevchenko
BBC Monitoring

I am still struggling to come to terms with the all-too-familiar towns in my home region being mentioned in world news, for all the wrong reasons.

Orikhiv, Vasylivka, Melitopol, Berdyansk, Tokmak are all places where our colleagues from BBC Verify have located Russian defences - but I remember them as sleepy, leafy places where time goes slowly and nothing mych happens.

Zaprorizhzhia region relies on farming heavily, and in most towns and villages work is scarce.

Many, if not most, young people there might hope to find employment in the regional centre, Zaporizhzhia - a move to Kyiv may well seem to be a very far off ambition.

As reports of expected offensives and counter-offensives abound, many of them will be fearful of being caught up in the fighting again.

Do military analysts help you?published at 13:48 British Summer Time 22 May 2023

13:48 BST 22 May 2023

Here's another question from one of our readers.

Gareth Pugh from Herefordshire asks whether we use military analysts to better understand the reasons why Russian defences are formed in a certain way.

Erwan Rivault replies:

Yes. For this report alone we were in touch with two analysts, who helped us understand a bit more about the Russian fortifications we could see on satelite images.

As we reported a little earlier, Mark Cancian from the Center for Strategic and International Studies explained that minefields, which Russians have used extensively throughout the war, were likely to be hidden between Tokmak's three defence lines.

Also, as we looked at the defences on the beach in Crimea, we discussed them with military experts who suggested they are likely to be a precaution, rather than a sign that Russia expects to defend a seaborne assault, since Ukraine has little naval capacity.

We also pull on the expertise from colleagues in our own team, like Tom Spencer, who contributed to the findings in our report.

Vitaly Shevchenko
BBC Monitoring

Image source, Reuters

As we've been reporting, Russia is has been fortifying its defences ahead of an expected Ukrainian counter-offensive.

But parts of south-eastern Ukraine likely to see most of the fighting during this push (or a new Russian offensive) are still home to a significant number of civilians. It's all but impossible to calculate exactly how many though, at a time of war.

There have been reports of evacuations allegedly being carried out by Russia-installed authorities in occupied areas of Zaporizhzhia region in anticipation of a Ukrainian counter-attack, but they have not been confirmed and, again, the numbers involved are unclear.

Yevgeny Balitsky, the man installed by Russia as regional “governor”, claimed on 16 May that 3,579 people had been relocated.

Shelling is not unusual in these areas, but with the exception of Donbas in the east, most of them have not seen active offensive actions on the ground for months, and their resumption would make things much worse for whoever still lives there.

Earlier this year, I was able to speak to residents of Mariupol, a city in Donetsk region captured by Russia a year ago after months of devastatingly fierce fighting. Even those with pro-Ukrainian views told me they feared that a Ukrainian counter-offensive would shatter their newly-found sense of relative safety.

Erwan Rivault
BBC Verify

Image source, .

Putting together different pieces of the puzzle is a large part of our job, as my colleague Daniele Palumbo said a little earlier.

Satellite images gathered over time allow us to spot trends and patterns.

But why don't we just go there and do the mapping ourselves? Well, there are a couple of hurdles, particularly in an active war zone.

Safety is the most obvious factor, as the areas we analysed are incredibly dangerous. Instead of being on the front line, I can trawl through data from our newsroom in London and corroborate information from different satellites - both open source and commercial.

Reporters and correspondents have been feeding back information to our newsroom, but as individuals they wouldn't be able to map every coordinate in Ukraine. Even if war wasn't a factor, it's a tremendous task that would take a very long time.

As satellites are in orbit, taking pictures of the entire planet, our analysis of their images relates to the whole of Ukraine, not just one specific region that a correspondent would be deployed to.

Satellite data has significant benefits, but there are some limitations that we should not overlook.

Cloud cover is our main challenge. For example, for a couple of weeks in April it was very cloudy and satellite images were useless because we couldn't see anything below the clouds.

But at the beginning of May, Ukraine had clear skies making it much easier to spot patterns in the terrain. That's when most of the images in our story are from, as we wanted to show the most up to date information.

Our next question is from Arthur Manning, from the US, who is asking if we are able to pinpoint ammo dumps, fuel stockpiles and equipment yards from satellite images.

Erwan Rivault replies:

It is indeed possible to identify and locate these from satellite images, but this was not part of our research. We focused instead on fortifications, such as trench networks and ditches.

However, if you wanted to spot fuel stockpiles for example, they have a recognisable cylindrical shape that can be easily identified.

Ammunition dumps are often stored in buildings. As satellite images give us a bird's-eye view, it is hard to interpret what is inside a building using images from the building's exterior. So even if we had good reason to believe ammunition was being stored at a certain coordinate, satellite images wouldn't be able to confirm or deny this information.

Vitaly Shevchenko
BBC Monitoring

The governor of Russian Belgorod region, Vyacheslav Gladkov, says a group of Ukrainian soldiers has crossed the border into his region, which lies just north of Ukraine's second city, Kharkiv.

"A reconnaissance and subversive group of the Ukrainian armed forces has entered Gayvoron district. The Russian armed forces together with the border force, National Guard and FSB are taking steps necessary to liquidate the enemy," he said on Telegram., external

Videos circulating online, external appear to show military vehicles - including a US-made Humvee of the type used by Ukraine - entering Russia’s Gayvoron checkpoint on the border with Ukraine.

The BBC has confirmed the location shown in the videos by comparing the distinctive buildings shown in them to those in publicly available satellite imagery showing the checkpoint, external. We have also confirmed they were uploaded earlier today by using software which checks them against existing videos on the internet - it found nothing posted before today matched them.

Ukraine’s Main Intelligence Directorate (GUR) has confirmed that an operation was under way in Belgorod region, and said that it only involved units comprised of Russian nationals fighting for Ukraine.

“The Russian Volunteer Corps and the Freedom of Russia Legion, which comprise Russian citizens, have today started an operation to liberate these parts of Belgorod region from the so-called Putin regime and push the enemy back to create a certain security strip to protect Ukrainian civilians,” GUR spokesman Andriy Yusov told Suspilne TV, external.

In the past, Ukraine has generally neither confirmed or denied operations that appeared to target Russian territory.

What about Ukraine's defences?published at 13:22 British Summer Time 22 May 2023

13:22 BST 22 May 2023

Daniele Palumbo
BBC Investigative Journalist

Shoukair asks: Do you also have data about Ukraine’s defence? If yes, can we have an insight on it?

Daniele says: We have been focusing on the Russian defensive lines as they are so big they are clearly visible from space. As they have been recently developed they have significantly changed the environment - an image from today greatly differs from an image a few months ago.

Furthermore, the Ukrainians are currently in an attacking position and as such their focus is more on advancing, rather than keeping their current positions.

Ukrainians also know their own territory better than the Russians and may use certain locations to their advantage.

We have, however, been tracking what equipment Ukraine is receiving for its future military operations.

What tactics can Ukraine use to breach Russia's defences?published at 13:18 British Summer Time 22 May 2023

13:18 BST 22 May 2023

We'll turn now to some more of your questions.

Bernie Keenan asked: What tactics can be used to breach defences (ditch/mines/dragons teeth) of the type described?

Our Security Correspondent Frank Gardner looked at this earlier, saying Russia's defences of deep trenches, minefields, gun positions and concrete ‘dragon’s teeth’ obstacles will not be insurmountable.

Over time, it's likely Ukraine will be sending armoured engineering, mine-clearing and bridging vehicles to go along with its advance.

However, any delays will allow Russian artillery, missiles and possibly air power to target Ukraine’s forces as they wait to advance.

Until Ukraine makes its advance, it will likely use long-range missiles to attack Russia’s rear logistics, targeting its fuel and ammunition depots and its transport hubs, in an effort to undermine Russia's defences.

Image source, Reuters

We'll just step away from looking at the BBC's satellite analysis of Russia's defences to look at what's happening on the ground in Ukraine today.

The Ukrainian city of Bakhmut which has seen fierce fighting between Ukrainian and Russian sides for months and we've had conflicting claims over the weekend.

Today, the head of Russia's Wagner mercenary group, Yevgeny Prigozhin, has vowed to transfer control of Bakhmut to the Russian army by 1 June. It comes after he claimed to have captured Bakhmut on Saturday.

Prigozhin said that Wagner had set up "defence lines" on the west of the city ahead of the transfer on Thursday.

But Ukraine's Deputy Defence Minister, Hanna Maliar, reiterated that its forces still have a small foothold inside the city and are advancing on the outskirts, adding that the "intensity" of their movement had reduced.

Analysts say Bakhmut is of little strategic value to Moscow, but its capture would be a symbolic victory for Russia after the longest battle of the war in Ukraine so far.

Read more here.

Erwan Rivault
BBC Verify

As Daniele just explained, verifying content is essential, particularly when it comes from social media. But what does it mean to verify something?

For example, when reports of an explosion start flooding across social media, Daniele and others will look at the landscape visible in the footage - trees, rivers, buildings and even power lines.

They will look at publicly available satellite images to try to match features from the social media content - a distinctive roundabout or a bend in a river, for example - to identify the location. This is called geo-locating, and they will then identify coordinates of the site.

Then I jump in, comparing the most recent and historical images of the location from commercial satellite companies.

Sometimes images can be just a few hours old. So in the case of an explosion, for example, we would be able to see it from space as black smoke.

But if there is any cloud cover, verification through satellite imagery would be impossible that day.

In this case, we would wait until there is a clear day and compare it to images available before the explosion. The key things we would look out for in this case would be damage to buildings, or any significant holes or unusual changes to the landscape.

Image source, .

Daniele Palumbo
BBC Verify

While satellite imagery is important, it works alongside the content we gather from social media. Verifying videos and images - checking exactly what they show, and when and where they were taken - is essential to understand what is going on in a specific area.

We are able to verify many videos and images every day. Often, we also see false claims of images said to be from Ukraine, also known as disinformation.

For example, last week we saw footage of an explosion which was said in social media posts to be in Ukraine, but it was actually from an explosion in 2007 in Iran.

Image source, Twitter

Another instance was after the Russian army shelled a Ukrainian ammunition depot. This involved many Twitter accounts claiming the increase of radioactivity in the area. We were able to verify that they were false claims by analysing radiation data from the European Union.

These two examples demonstrate the importance of being able to scrutinise every single detail when breaking news happens. Only by verifying this content are we are able to link facts to images.

Image source, .

Paul Adams
BBC Diplomatic correspondent

Throughout the winter and spring, Ukrainian troops have clung on to front line positions with grim determination and at great cost.

All the while, fresh units have been getting ready, preparing to take the initiative once more.

At least eight new brigades have been put together: around 40,000 troops, many of them trained in the West and equipped with an array of advanced equipment, including hundreds of tanks and other armoured vehicles.

All along 600 miles of front lines, Ukrainian commanders will be looking for points of Russian weakness. While cutting Russia’s land bridge to Crimea would appear to be Kyiv’s most logical objective, commanders will also want to keep their opponents guessing.

There won’t be a starting gun for this offensive. In all likelihood, it’s already begun.

New long range weapons like the British-supplied Stormshadow missiles have already been used to attack key targets far behind Russia’s defensive positions, in an effort to make life as difficult as possible for troops on the front line.

Image source, .

Could journalism like this help the Russians?published at 12:33 British Summer Time 22 May 2023

12:33 BST 22 May 2023

Daniele Palumbo
BBC Verify

Peter, Buckinghamshire asks:

How much could analysis like this help the Russians? I watch pundits offering possible attack/defence scenarios with dismay. Surely they will be using all media offerings as potential spying sources.

Daniele Palumbo answered:

This story does not help Russia because it uncovers what the Russians themselves have been building since October 2022. So, this type of analysis only helps the reader to understand the real dynamics of the conflict and how the war is being fought.

Something to bear in mind is that both the Ukrainian and Russian army have their own intelligence units, so it is possible that they know more than we at the BBC do.

In addition, it is important to note that media organisations are at times are restricted from disclosing the locations of certain events for security reasons.

For example, if there is a missile attack in a residential area, we are not able to disclose that location for three hours because it may help the Russian army to plan a more precise strike.

What satellite intelligence is Ukraine using?published at 12:27 British Summer Time 22 May 2023

12:27 BST 22 May 2023

Next up in our questions from readers is Brian Mills, in the USA, who asks:

Assuming both Ukraine and Russia have access to similar satellites and their geographic information system (GIS) mapping capabilities, what are the Ukrainian options?

Vitaliy Shevchenko answered:

Satellites are important eyes in the sky to have for both Ukraine and Russia. While Russia has launched numerous military spy satellites of its own, Ukraine has been making use of commercially available imagery showing Russian positions on the ground, as well as important radio electronic data collected by satellites, such as signals emitted by Russian radars and GPS jamming stations.

Western allies have also reportedly been sharing satellite intelligence with Ukraine - but exactly what is a closely guarded secret.

In an interview with the BBC, the head of the US Space Force, General Jay Raymond, described the Russia-Ukraine war as the "first war where commercial space capabilities have really played a significant role". It's also the first major conflict in which both sides have become so reliant on space, he said.

Ordinary Ukrainians take this type of intelligence so seriously that they crowdfunded access to a commercial Finnish radar satellite, external, reportedly worth more than $16m.

Can satellite images show where mines have been laid?published at 12:21 British Summer Time 22 May 2023

12:21 BST 22 May 2023

We'll now turn to the first of our questions from readers for Daniele Palumbo, Erwan Rivault from BBC Verify, and Ukrainecast presenter Vitaly Shevchenko.

Ismo Anttila from Finland asks whether satellite images show us whether mines have been laid in the area.

Erwan Rivault replies:

Well, from the satellite images we analysed it is not possible to say whether mines have been laid. They are just too small to spot and are designed to be difficult to see.

However, it is common practice to hide landmines in defence positions.

As Mark Cancian from the Center for Strategic and International Studies told us, it is highly likely that mines have been hidden between the Tokmak's three defence lines. So, if there are any mines, Cancian says they would be between the anti-tank ditch and the trench network.

Image source, .

Cancian also told us minefields are a standard part of every defence, and the Russians have used them extensively throughout the war.

Vitaly Shevchenko
BBC Monitoring

There are three major general directions in which Ukraine is likely to counterattack: Donbas in the east, Zaporizhzhia region in the south-east and Kherson region in the south.

Of them, parts of Donbas (i.e. of Donetsk and Luhansk regions) have spent the longest time under Russian occupation after first being targeted in 2014, and this is where Russia is most entrenched in terms of both its military and political presence.

If Ukraine’s counteroffensive in Zaporizhzhia region is successful, its troops can potentially reach the northern shore of the Azov Sea, divide Russian troops stationed along it and significantly complicate logistics for the Russians.

This would also put the Crimean peninsula – another, hugely important part of Ukraine occupied since 2014 – within easier reach for Ukrainian forces.

Making gains south of Kherson would mean crossing the wide Dnipro River to face Russian troops dug in on its other bank, but one of the main prizes of this risky and difficult manoeuvre is the possibility to advance on to Crimea – whose annexation is a matter of immense pride for President Putin.

Image source, .

Heather Sharp
Live reporter

If you're just joining us, welcome to our live coverage looking at our report on how Russian forces have been building up their defences in Ukraine.

It's been put together by the BBC Verify team - our team of journalists who trawl through imagery, videos and data to work out what’s happening and challenge disinformation.

With me are the authors of the article, Daniele Palumbo and Erwan Rivault, who are talking us through what they discovered and how they did it.

Together with Ukrainecast presenter Vitaly Shevchenko, they will be answering your questions here too.

We're also keeping an eye across what's happening on the ground in Ukraine today. Stay with us.