Washington DC's Isometric Map Grid
East and West
Since these four points and the WH are located at the vertices of the pentagram, we can safely say that the relative east west positions of the vertices of the pentagram determines the scale of the map west of the CB.
North and South
We are told that the distance between the House of the Temple and the Jeff Mml is 3600 meters, which is the same as six 600 meter sections; we can use a circle drawn around the WH to the HOT or JM to determine the position of the third line from the WH. We can also use a circle to establish a line 2400 meters west of the WH to complete the symmetrical distribution of lines. (Note that this line, which we will label 32, as in twice 16, crosses Roosevelt Island very near the light spot there.)
Another circle shows that the tip of the 'triangle' (where New Hampshire crosses 16th St) and the WH are equidistant from Scott Circle. We establish three horizontal (E-W) lines at these positions. [Note that the light spot on the island is very near where the E-W WH line crosses 32.]
In the next image Penn Ave and NY Ave are highlighted as rays from the WH, with Mass and Rhode Island crossing at Scott Circle. While the distance from Wash Cr to Mt Vernon Sq sets the east-west scale, the distance from the WH to Scott Cr sets the north-south scale in the western half of the map. All four of these avenues connect two of the corners of the pentagram, while 16th St connects Scott Cr and the WH. [Rhode Is intersects 32 at the E-W line from the WH, at the light spot on the island.]
Extending New Hampshire from the top of the triangle thru DuPont Cr and Washington Cr we see that it intersects the 32 line at the same place as NY Ave when it is projected southwest past the WH.
axes like we see in the Star of David, Metatron's Cube and the map.
Extending New Hampshire further across the Potomac (below), we see that it intersects with Memorial Avenue in Arlington which appears to run to the center of the Ellipse south of the WH at the same angle as the 'isometric' grid pattern.
On the right side of 16th Street, a line from the top of the triangle through Logan Cr and Mt Vernon Sq intersects the 0 line south of the current CB location, where the projected Penn Ave also crosses. You can use a circle to prove that this point is the same distance south of the WH as Scott Cr is north of it. We add another E-W grid line here.
The CB and Jeff Mml
As you can see, it is not true as it says on this page that, "the Capitol Building is right on the spot where the other 52-degree line ends at the base" (meaning 'of the triangle'). He is also wrong about Penn Ave being straight from Georgetown to the CB, as it clearly has a bend in it at the White House. Attempts to make the CB fit the grid of the north half of the map fail here.
We can use a circle to show that the line from the Pentagon crosses 16th Street at a point the same distance from the WH as the top of the triangle is. We add another E-W grid line here.
The CB and Jeff Mml (purple circle) appear to be north of their 'ideal' locations as determined by the grid(s).