faster estimate or not really? https://github.com/OpenTTD/OpenTTD/blob/master/src/pathfinder/yapf/yapf_ship.cpp#L97-L123

PfCalcEstimate.cpp

/** Original code: https://github.com/OpenTTD/OpenTTD/blob/master/src/pathfinder/yapf/yapf_ship.cpp#L97-L123 */

  /**
	 * Called by YAPF to calculate cost estimate. Calculates distance to the destination
	 * adds it to the actual cost from origin and stores the sum to the Node::m_estimate.
	 */
	inline bool PfCalcEstimate(Node &n)
	{
		if (PfDetectDestination(n)) {
			n.m_estimate = n.m_cost;
			return true;
		}

		const TileIndex destination_tile = m_has_intermediate_dest ? m_intermediate_dest_tile : m_destTile;

		extern const TileIndexDiffC _tileoffs_by_diagdir[DIAGDIR_END];
		static const int YAPF_HALF_TILE_LENGTH = YAPF_TILE_LENGTH >> 1;

		TileIndex tile = n.m_segment_last_tile;
		DiagDirection exitdir = TrackdirToExitdir(n.m_segment_last_td);
		int dx = std::abs(((int)TileX(tile) << 1) + _tileoffs_by_diagdir[exitdir].x - ((int)TileX(destination_tile) << 1));
		int dy = std::abs(((int)TileY(tile) << 1) + _tileoffs_by_diagdir[exitdir].y - ((int)TileY(destination_tile) << 1));
		n.m_estimate = n.m_cost + std::min(dx, dy) * YAPF_TILE_CORNER_LENGTH + (std::abs(dx - dy) - 1) * YAPF_HALF_TILE_LENGTH;
		assert(n.m_estimate >= n.m_parent->m_estimate);
		return true;
	}