John Rostron

The advantage is having a duplicate underneath so any adjustments on the master layer (top) can be brushed out with a mask revealing the unmodified layer below.

Thanks for the responses ...
Below image shows the various layers and the "trail" I see when all selected. I too think this has something to do with feathering of the edge ... but so far nothing I have attempted has worked. Did not delete the sky layer and start over, just tried modifying the selection settings via select->feather, select-refine edges, select->smooth, but these don't seem to "take". For example I select the sky layer, select->feather, set 5px, hit apply, go back into select-feather and the px is back to 0. I am probably trying to modify the selection properties in a way that can't be done after the selection has been created? As I said, I am new to Affinity .
I will take a shot as deleting the sky layer and recreating it with feathering ... 
 

Thank you both for your quick responses, I will let you know how I got on when I get back to my laptop later.

I thought of that originally, but when I came to write my second suggestion, I couldn't remember it. So I wrote my third thought!
I have a Senior Moment sign in front of me as I write!
John

Hold off revising your macros.  If it was degrees in 1.6, we'll make that the default.  I'll add the options to use Radians at a later date.

Well, . . . I've done it again. It seems like, on this forum and others, every time I can't figure something out within 10 minutes - I create a new thread. After the thread goes public I go back to the app and try a few of my own ideas . . . (of which I have no idea where I get the ideas from) . . . while I wait for forum replies. Then, strangely, I seem to figure it out. So, I go back to post my own discovery and find that Psenda and John Rostron suggest the Mesh Warp Tool. Wow, how coincidental - I had just found that out for myself.
Henceforth - in the future I have decided to trick myself. I will open WORD and type in an imaginary NEW TOPIC. Then I'll save it to my desktop. Then I'll go back to said application and discover my own solution. . . . Unreal!

I've posted on your other link re the use of trig functions.
 
There have been some changes - trig functions either must take angle values, or now return angle values.  This currently defaults to dealing in degrees, not radians.  I can't recall now what the trig functions used to do.  I have made a lot of changes between 1.6 and 1.7 to expressions - unit types have been tightened up.  ie, distances and angles cannot be mixed up.
 

All quiet in the garden just now; the dandelions are starting to seed. I've been waiting for one to practice on.

@jessicahopemedlock, you are not the first to solve a problem immediately after posting it. Many have gone before you. However it would help if you outlined in detail what you thought was the problem and how you resolved it. This would help others who might think they had the same problem.
John

I didnt realise the file in affinity designer was in pixels, and the original file was in cm, created in photo. When i changed the designer file to cm it was as it should be! 

I have just read the entire thread cited by @stokerg an I am minded of the famous dialogue from Alice Through the Looking Glass:
John

I have just read the entire thread cited by @stokerg an I am minded of the famous dialogue from Alice Through the Looking Glass:
John

I have just read the entire thread cited by @stokerg an I am minded of the famous dialogue from Alice Through the Looking Glass:
John

I have just read the entire thread cited by @stokerg an I am minded of the famous dialogue from Alice Through the Looking Glass:
John

I cannot explain why, but have you tried inverting the pixel selection, then just deleting the now-selected background?
John

Hi creatinglightly
For the selection you're making I'd recommend using the Selection Brush Tool as using flood/wand selections will select like-pixels by colour, rather than edge detection. It looks as though the colours in the arm are close to some of the tones in the pebbles and this is my you're selection has 'mist' around it.
Try deselecting and using the Selection Brush Tool, as this will use edge detection to select the arm only

Thanks very much!

Yes, worked, but only if not ticked from the beginning of a session.  Annoying since ticked is the default.  
But note the behaviour is inconsistent since the first batch job works even when Parallel Processing is ticked, but subsequent batch jobs do not work - even if not ticked, so then you have to force quit because the batch job runs in the background and never finishes.  
Thanks for taking the time to answer.
Julian.

Thanks for this I'll take a look at it ....

All of you are wrong answer. You did not check on Macintosh only. I am not use Windows.

As far as I can see, the rectangles themselves do not have any visible component, so you would need to blur the fills. Would you be able to blur the bottom edge of the top concrete image and the top edge of the bottom fill. It is difficult to be precise without knowing the details of the various objects.
John

Thanks @Pšenda, I thought that I was probably re-inventing the wheel.
John

Yes, I'm pretty sure that the solution posted some time ago was not the one I came up with. I still cannot remember what it was. So I had to re-invent the wheel by myself. I cannot remember for sure, but when I came up with my solution, I was not aware of others having invented it for themselves. This does not imply that there were not any such inventive users.
John

Perhaps I misunderstood your comment, John! If so, please accept my apologies.
I thought you were saying, in effect, that someone posted ‘your’ solution but you couldn’t find their post, so you had to work out the solution for yourself: I adopted the ‘colon space’ solution as soon as I read about it elsewhere. Are you actually saying that you think there’s a different solution?