Bohlman - On Orbit - Bohlman, Saratoga map

Statistics:

Max. grade: 22% (24% on inside of right turn)
Main climb:
Avg. grade: 9.0% (elev. gain/dist)
Length: 4.11 miles (6.61 km)
Elev. gain: 1950 feet (594 m)
Entire profile:
Avg. grade: 9.8%
Length: 4.39 miles (7.06 km)
Climb: 2100 feet (640 m)
Descent: 170 feet (52 m)

Description:

Dan Connelly describes it well:

This is really, really, hard on standard road gears. The listed stats show a steep average grade of 8.9%, but there is a considerable flat section at the top, so it is actually much worse than this. A low gear of 39/28 or lower really helps here. On Orbit Dr is an alternate route which bypasses a section of Bohlman. To capture the full effect of this climb, On Orbit should be taken, as it includes significant sections at near 20%.

From the top of Bohlman, if you survive, there is a 0.9-mile dirt road to the right (bear right on the dirt) to the top of Montevena Road, which can be descended to Highway 17. A short trip to the right along Hwy 17 brings one to Black Road, which can be climbed to Skyline Road. After B-O-B, the 10% grades of Black Road are cake.

Altimeter altitude

(Altitude linearly interpolated from altimeter samples, and smoothed with a 0.04mi gaussian.)

Each horizontal line is 100 feet. Each vertical line is 0.2 miles.

Gradiometer grade

(Grade linearly interpolated from gradiometer samples, and smoothed with a 0.04mi gaussian.)

Each horizontal line is 2% grade. Each vertical line is 0.2 miles.

Altimeter grade

(Grade linearly interpolated from altimeter samples, and smoothed with a 0.20mi gaussian.)

Each horizontal line is 2% grade. Each vertical line is 0.2 miles.

Comparison of grades

(Green grade is from the gradiometer, magenta grade is from the altimeter, and white is where they overlap.)

Each horizontal line is 2% grade. Each vertical line is 0.2 miles.

Overall (averaging my first 20 hills), the gradiometer grade averages 0.63 (% grade) higher than the altimeter grade, with a standard deviation of 4.5 (% grade per road). This error may be due to:

In the end, though, I think that each individual sample is accurate to within about 2% for that instantaneous segment of road. My results may not always agree with my altimeter, but they are generally repeatable within 1%. I think that I just need to take more samples to generate more accurate graphs.

Raw Data: 

Dist    Grade   Alti.   Location
----    -----   ------  --------
0.00     1%	 640	start - 6th street
0.04	 4%	 650
0.07	 1%	 650	sister of Notre Dame
0.09	 8%	 660
0.11	 5%	 660
0.14	 4%	 670
0.17	 4%	 670	Hidden Valley Lane
0.20 	 6%	 680
0.22	 9%	 690
0.24	 5%	 700
0.26	10%	 710
0.28	13%	 720
0.30	14%	 730	Norton Road
0.32	11%	 740	sign: slow, one lane road ahead
0.34	12%	 750
0.36	11%	 760
0.38	10%	 770
0.40	11%	 780
0.42	13%	 800	left turn
0.44	16%	 810
0.46	12%	 830
0.48	13%	 850
0.51	14%	 860	sign: no parking any time
0.53	13%	 880	signpost: (sign missing)
0.55	12%	 890
0.58	13%	 910
0.59	12%	 920
0.61	13%	 930
0.62	12%	 940	right turn
0.64	13%	 950	15210 Bohlman
0.66	12%	 960
0.68	10%	 970
0.70	13%	 980
0.72	13%	 990
0.74	20%	1010	right turn -- 16% on the outside -- 15270 Bohlman 
0.75	11%	1020
0.77	10%	1030
0.79	12%	1040
0.80	11%	1040
0.82	11%	1050
0.83	12%	1060
0.84	18%	1060	right turn -- 16% on the outside -- 15280 Bohlman
0.85	11%	1070
0.87	11%	1080
0.89	14%	1090
0.91	13%	1100
0.92	11%	1110
0.94	12%	1120	Kitridge Road
0.95	18%	1130	right turn -- 10% on the outside
0.96	12%	1140
0.97	12%	1150
0.99	11%	1160	1535 Bohlman
1.00	12%	1160	left turn -- 20% on the inside
1.02	11%	1170
1.04	12%	1180
1.08	 9%	1200	
1.10	13%	1210
1.12	10%	1220
1.15	10%	1240
1.17	13%	1260
1.19	11%	1270
1.22	11%	1280
1.24	11%	1290	Belnap Way
1.26	17%	1300	straight
1.27	17%	1310	straight
1.28	16%	1320
1.29	 8%	1330	right turn
1.30	 7%	1340
1.33	 8%	1350
1.36	 8%	1360
1.38	11%	1370	Archibald Road
1.40	16%	1380	left turn (23% inside)
1.42	14%	1400
1.43	16%	1410
1.45	19%	1430
1.46	18%	1440	15515 Bohlman
1.47	24%	1450	right turn - 18% on the outside
1.48	20%	1460
1.49	15%	1470
1.51	12%	1480
1.52	14%	1490
1.53	15%	1500
1.54	18%	1500
1.55	16%	1510
1.56	 0%	1520	left turn -- 15525 Bohlman
1.57	 4%	1520
1.61	 4%	1530
1.64	 8%	1540
1.65	16%	1550
1.66	16%	1560
1.67	14%	1570
1.70	13%	1590
1.73	15%	1610	sign: ICY
1.75	16%	1630
1.76	12%	1640	---- On Orbit ----
1.78	 7%	1650
1.79	18%	1660
1.81	16%	1670
1.83	15%	1680	15520 On Orbit
1.84	12%	1680	right turn
1.85	14%	1690
1.87	16%	1700
1.89	16%	1720
1.93	18%	1760	15501 On Orbit
1.94	11%	1770
1.95	14%	1780
1.97	15%	1800
1.99	16%	1810
2.01	 9%	1830
2.04	 7%	1840
2.05	 3%	1840
2.07	 2%	1840
2.09	 8%	1850
2.11	 9%	1850	15550 On Orbit
2.12	21%	1860	right turn
2.13	16%	1860
2.15	14%	1880
2.19	14%	1910
2.21	18%	1920	right turn
2.23	19%	1940
2.24	22%	1960
2.25	19%	1970	15555 On Orbit
2.26	18%	1990
2.28	18%	2010
2.30	19%	2020
2.31	18%	2040
2.33	18%	2060
2.36	17%	2080
2.38	15%	2100
2.40	13%	2110
2.41	 7%	2110	15605 On Orbit
2.42	 0%	2110	Apollo Hts. Ct.
2.45	-11%	2100
2.48	-12%	2080
2.51	 -3%	2070
2.54	 -2%	2070
2.57	-11%	2060
2.59	-16%	2040
2.60	 0%	2040	---- Bohlman again ----
2.61	14%	2040
2.64	14%	2070
2.66	13%	2090
2.69	12%	2110
2.71	 9%	2120
2.75	 6%	2140
2.78	 8%	2150
2.80	12%	2160
2.83	13%	2180
2.86	15%	2200
2.88	11%	2200
2.89	 0%	2200	
2.93	 -1%	2200
3.00	 2%	2210
3.07	 -3%	2220
3.16	 0%	2200	16200 Bohlman
3.18	 7%	2210
3.19	16%	2210
3.20	16%	2220
3.22	13%	2230	right turn
3.24	 8%	2250
3.29	 8%	2270
3.34	 8%	2290
3.37	14%	2310
3.40	 9%	2330
3.42	13%	2350
3.44	13%	2360
3.46	 9%	2370
3.49	 8%	2380
3.51	12%	2400
3.54	11%	2420
3.56	11%	2430
3.57	14%	2440
3.59	12%	2450	16641 Bohlman
3.63	 8%	2470
3.65	10%	2480	Bay Springs Road
3.67	 5%	2490
3.70	 1%	2500	16654 Bohlman
3.72	 6%	2500
3.75	 4%	2510
3.76	 0%	2510
3.79	 -6%	2500
3.83	 -6%	2480
3.84	 0%	2480
3.90	 0%	2480	sharp right turn
3.91	16%	2490	16830 Bohlman
3.93	13%	2500
3.96	12%	2520
3.99	 6%	2540
4.02	 7%	2560
4.06	 9%	2570	16960 Bohlman
4.09	 7%	2580
4.11	 0%	2590
4.14	 -9%	2580
4.16	 0%	2570
4.17	10%	2580
4.19	 8%	2590
4.21	 0%	2590	Mc Gill Road
4.23	-7%	2580	Gravel, rocks on road
4.26	-4%	2570
4.31	 0%	2560
4.36	 4%	2560
4.39	 3%	2570	sign: END

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