That photo of the peas in the gutter is so cool. Do you slide them out into the garden?
The technique is called "guttering". It protects the seeds from any living things moving thru the soil that would normally eat the seeds and since you use growing medium instead of normal ground soil, drainage is much better so they don't rot.
You actually take them out and transplant them. I know there are a lot of gardeners who think peas can not be transplanted, but they absolutely can. You just need to do it properly and at the right time.
Do you use this method just for peas?
I forgot to mention:
Sweet peas germinate when the ground temperature is a uniform 55-65 degrees. Once germinated, the plants thrive at temperatures from 70 to 80 degrees. Above 85 degrees, they struggle. Start your plants six to eight weeks before you plan to transplant them.
You can use this method for any seed starting. It's just another form of a container. In this case it lends itself to a row of peas.
If you're seed starting now, I do recommend, as others have, to visit the Winter Sowing Forum. Read the FAQ first. It's a method that works. It's more efficient than traditional methods in multiple ways.