Peas can go in the ground 1-2 inches deep and 1-2 inches apart. They won't all come up. There is not a set standard for planting peas but they do need to be at least an inch deep but no more than two inches deep. They are probably planted the deepest of all seeds. You can follow the seed packs for thinning guidelines but they tend to over state the need for space.
Here is one method I use for planting peas and a baby greens patch. They are planted together in very limited space.
|Turning the Ground for Peas and Greens: Gary Pilarchik|
|Turned, Mounded and You Can See the Line of Peas: Gary Pilarchik|
|A Close Up of the Spacing for Pea Rows: Gary Pilarchik|
|Lettuce Seed Spacing for Baby Green: Gary Pilarchik|
|Row Peas Planted and Staked with Baby Greens: Gary Pilarchik|
|The Rusted Garden Blog Peas: Gary Pilarchik|